Just putting it out there, based on my testing -
1. KOF 02 UM is perfect, no hiccups nothing. Perfect port. For me, more or less does it for me since Switch lacks good old KOF ports with arranged music. Very playable (didn't even notice any drops in frame drops during character selection) - do note I am using the translated ISO.
2. KOF 98 UM runs Ok, occasional slowdown when things explode with a bunch of sprites. So, I don't think it's playable (since it lacks the speed of KOF 02, these games are all about speed). Some might be able to tolerate specific slowdowns to about 20 frames. With LSFG enabled (if you turn on frame generation), picture will get stuck at a single frame.
3. KOF 94 Rebout - Runs at about > 30 fps, until you fire a projectile and then it slows until that projectile is omitted from screen, other than that, playable.
4. WWE Smackdown Here Comes the Pain, videos about 10-15fps - in game, 15-20... will drop to 10. With LSFG enabled (if you turn on frame generation), picture will get stuck at a single frame. Not playable.
5. Shadow Hearts 1 - Slow, about 10-20 fps, then will randomly crash (new NetherSX2) - I also tried the older NetherSX version, also crashes (and is pretty slow). Not playable.
6. Marvel vs Capcom 2 - Perfect, some selection screen slowdown but runs perfectly. Plus compression costs just about 200MB of storage space - even better than the official Switch port!
7. Capcom vs SNK 2 2001 - Perfect, 30fps standard. Compression costs just over 200MB. Storage cost is even lower than official ports.
8. KOF XI - runs well, menu screen/selection screen drops by a couple of frames, but generally 30 fps - playable.
9. NeoGeo Battle Collisium - As suggested by the above gentleman, playable, menu/character selection minor frame drops, but on the whole 30 fps consistently - playable. I didn't want to list this here as it is already done above - but since I downloaded it and added to my library... might as well list it.
Also, I put in the Lossless dll in the folder, tried to enable frame generation - in games, it will just get stuck on a single frame. Not sure if this is working, will need more work. I disabled it generally because games began crashing. Ultimately, I had to disable lossless frame generation because games would just crash. Even good ones.
I don't think heavy 3D games will be playable - but the above kinda addresses a lot of Switch shortcomings for me, MvC2 / KOF 02 UM / CvSNK2 - I can remove the heavy Capcom collections (about 3-4 gb each) from my SD card, since I already have retroarch, I don't need any of those. Plus the Gzip compressed copies of CvSNK2 is about 200MB! Same for MvC2 - 200MB+. Compare that with an actual Switch port of 3-5GB each. Certainly worth considering replacing if you're only offline like me.
Hope this is helpful. I was also wondering if someone could advise on how to update covers? I tried game codes as jpg/png files couldn't do so - and also tried file names without extensions... also couldn't do so.
Thank you Naga for the port - use AI (if you're not already using it) to try and refine whatever open code you've got access to. Though given AetherSX2 was closed, not sure how much of it can be optimized, not sure if someone has tried to reverse engineer that apk... but well, this is excellent progress! I am just happy to see KOF (98 was also something I wanted, but you can't have everything!) ports. The access to PS2 libraries is a big big deal for Switch owners.
No need to invest in one of those stupid Chinese devices for PS2 ports!