For me, the best traits of CCG's are variety and experimentation.
How much $$$ you need to spend to get your variety ? CAN you even get it ? Those are the important questions for me.

I quit playing Heathstone LONG ago just because I am not going to play 60 (!!!!!!!) games for five cards, one of them uncommon.
And buying pixels for real and very considerable money doesn't sound good either. Moreover, it's mechanics themselves restrict that: classes are fixed and can't be mixed, and are also pretty similiar due to not being fully defined, build-around cards are very few, and most of them are either super-ineffective or blatant and therefore boring, all decks play essentially the same game and aggro-midrange-control aren't even so different. Also, there are NO tutors.

Is there any digital CCG out there that would be friendly to different (!) jank (!) (and non-jank) strategies and have a reasonable reward rate ? I wouldn't mind Pay-To-Play OR generous Free-To-Play.

I have sunk 251 hours into Eternal and have a complete playset of all of the commons and uncommons, a complete one-of of all the rares, and 71% of the way to having one-ofs of all the legendaries. And I only spent 3 dollars on it to get a bonus which states I will get three packs of each new set when it releases for the rest of time. Beyond that one-time payment of money, I have spent no money on the game and reached Master rank in Gauntlet (a free, one-player game mode which gets harder the more you win in it and can yield a maximum prize payout of three silver chests), Master rank in Forge (a one-player game mode that is akin to drafting that costs 2500 in-game gold, and you get to keep the cards you pick to make a deck out of, maximum prize payout of three gold chests), and have varying degrees of success in the Ranked and Draft game modes (which are both PVP; Ranked is free to play, Draft is 5000 gold and you draft from four packs). Over the course of three wins in Ranked, you get two copper chests and one silver chest. Maximum payout in Draft is three diamond chests, and a minimum payout of two silver chests (whereas the single-player game modes have a minimum payout of nothing). At the end of each month, your Ranked and Draft ratings are reset and you get three event chests with prizes based on your rating. I've ended with copper rating enough times to have found out you get two premium commons and a pack.

Copper chests yield 20-50 gold and a random common, silver chests yield 220-325 gold and a random uncommon, gold chests yield 500-600 gold and a pack, and diamond chests yields 2000-4000 gold, a pack, and a random premium (animated) card. With exception to event chests and rank-up chests, every chest has a random chance to upgrade into the next tier up. I have only been lucky enough once to have a copper chest upgrade into silver chest, which upgraded into a gold chest, and then upgraded into a diamond chest. It was awesome. I don't remember what a rank-up chest has in it. I think 1000 gold and a pack.

Oh, and last tidbit of information: you can create individual cards using a thing called Shiftstone. You get 100 shiftstone from opening one pack of cards, 1 from destroying a common (25 if premium), 10 from destroying an uncommon (50 if premium), 200 from a rare (800 if premium), and 800 from a legendary (3200 if premium). It costs 50 shiftstone to make a common card (800 for a premium version), 100 for an uncommon (1600 for premium), 800 for a rare (3200 for premium), and 3200 for a legendary (9600 for premium). You can basically trade a premium rare or legendary for its non-premium version if you want. I honestly suggest saving shiftstone to create rares and legendaries, because you will get way more copper and silver chests than any other type of chest over the course of you playing this game. You've missed several promos, but you can still make them for 600 shiftstone a card (2400 if you want premium versions).

Also, fair warning: they're about to release a new set soon, so if you want six "free" packs I'd get the game soon and spend that 3 dollars. You get 300 Gems for your investment, which can be used for various things in-game (most affordably, packs, which you can buy for 1000 gold or 100 gems). You have to play through a campaign mode tutorial before you can do other game modes, and there's a second campaign that costs 20k gold or 1k gems to unlock, which yields playsets of 16 unique cards. If you don't feel like grinding for the gold, you can spend 10 USD to get 1100 gems instead (you get the bonus packs for any purchase of gems, not just the 3 dollar one).

Oh yeah, and you get 12 cards per pack. One rare or legendary, 3 uncommons, and 8 commons. Cards have a random chance of being premium.

I keep forgetting things: You get daily quests which you can complete to get chests. So far the only quest payouts I've seen are two silver and one gold. I prefer the silver ones because of that slim chance that both will upgrade into gold chests.

Money, money, money,
Always funny
In a rich mans' world !

What about creativity, combos, build-arounds, strategic variety, jank ? That kind of thing ?

You can build your own decks (after finishing the tutorial), mixing and matching any factions you want (similar to how you can build decks in Magic). Right now the prevailing deck is Warcry, but if you're not hellbent on winning all of the time in PvP there are plenty of other strategies to pursue. Aggro, burn, graveyard recursion, lifegain out the wazoo, weenies, fliers, some tribal (Yetis are especially fun with the promo lord and you can get a Dinosaur lord out of the Jekk's Bounty campaign). Pretty much every legendary card is a build-around card, but there are other things that you can build around (my favorite is Hero of the People, an uncommon; when you play a unit with what is known as a "battle skill", Hero of the People gains that skill and gets +1/+1 for each battle skill it has). Plenty of comboes (Vara + Slumbering Stone + sac outlet is very fun). There's also a cycle of cards which are free once you meet a certain condition. Two of them are rare, three are uncommon (one of them actually just has a cost of 0 but requires you to get three influence of the Time faction, but it fits the theme of the cycle so I count it as part of it).

It's free to play, just try it and if you don't like it uninstall it. I think you can play the tutorial campaign without committing to making an account for it (it was a feature added after I started playing, so I don't know the details). You start off with a single faction deck in the tutorial, but as you progress you'll get more cards and can eventually mix and match them to make your own deck to play through it. The final battle int he tutorial campaign is a deck only available in that battle. Jekk's Bounty also has a few battles where your deck is replaced by one specific to the battle (there's one that's always just a mish-mash of random cards, it's really fun to play).

You're asking me to quantify something I don't know how to quantify, so if these don't answer you the way you want answers, then I'm sorry. Not to mention that "jank" is such an opinionated word. If you consider Nacatl War-Pride to be a jank card, then I'm the wrong person to be asking about what jank Eternal has.

Note: I call it a tutorial campaign, but it's really just the first four battles that are the tutorial. There are 21 battles in total.

That write up is jank

That's to be expected, as my articulation skills are jank.

All ccgs cost a lot of money unless you are good at farming draft.

The pokemon tcg has a pretty good online platform thats free qnd actually pretty easy to farm and trade. I had a tier 1 extended deck pretty early since it was mostly uncommons.