Thank you, I actually red (found online) the "release notes" about the evolutions going on (this one: FUT Birthday and "Make Your Idol" one) where they specify which cards are suitable to Evolve, apply playstyles etc. and if I got it right, it's mentioned there as well.
But this is NOT so clear, it's almost made on purpose I would say. Doesn't seem fair or clear. I'm not totally unhappy with this Evolution (Osimnhen 87 base card) that I mentioned before, even if I didn't try it yet after evolving it. Just that I chose it upon counting on being able to add and "customize" some more playstyles which turn out not to work... as it seemed.
Being the only difference a slight outline cosmetic/graphic and its designation, which are mentioned in some hidden footnotes somewhere in the official site, not in the game.