Some classic, decent sprite animation, goated GenesisKeys tune also ofc.

My money, I'd go with demo 3. Kyo and Jin (that specific Jin spritesheet in particular) seem like they'd have the most interesting choreography, pretty dynamic and technical fighters the two of em. If you're worried about the gap in projectile ability you could always look at some of the stuff that Jin can pull of in SFxT.

Even though I get the concept for Kula and Sub-Zero, their combat style would have pretty stark opposition. Sub-Zero would probably rather fight Glacius from KI, and Kula would probably rather fight somebody like Rimururu from SamSho. Either of them could probably be comfortable fighting Kolin from SFV since she's got a more militaristic, and therefore neutral fighting adaptation with her ice powers. That being said, to my knowledge nobody has made a full back-port sheet for Kolin, which is a bit of a shame.

As for Scorp v Shinnok, it's just a bit less exciting since it's same universe i.e. you could make the match happen in the many games they really share.