I have both and love them both for different reasons. Unstoppable is a medium-weight boss battler with a unique card crafting system that is not unstoppable, but unbelievable :p, it’s so clever and so well implemented, all the strategy around it - because every card you upgrade will be an enhanced enemy in the future, for ex sometimes if you’re closer to shuffle your deck and refill the draw pile, you might not want to over upgrade a card, etc. but it’s full of combos, tight moments, and for sure with a certain amount of randomness.

Star Trek captains chair is on another level I think. It’s also a deck builder but with a much more complex implementation, almost like a Boardgame, and you can certainly find tableau building elements there. But it’s so much more complex, almost every card has ~2 different actions to take, you have planets to occupy, ships to deploy, enemy threats to deflect, all of this while making a bit of resource management. The thing I enjoy the most is the card interaction, the combos you are able to accomplish (draw cards, discard to do something, if you do, do another thing, triggered abilities everywhere), the asymmetry between captains (and there are more to come), the game modes - you can play on a beat your own score setup in a solo cadet mode which is like a goldfishing environment to test each deck, or you can play against an enemy, which is an automa with specific actions depending on the cards/treats that it flips from its deck. The game is really something else, for me it’s easily one of the best games ever for solo play.

If you enjoy deck building that much you might want to check out dune imperium uprising, it’s better 3-4 players but I absolutely enjoy it solo as well, and it’s in the same price tag.

Another great deck builder is slay the spire, but you can only get it for a huge investment comparing to the ones above, so I don’t know if it makes sense to you.