If you want something really cheap while waiting or deciding which real option to go with this thing has actually been really good to me for the price. No extra features though:
https://www.amazon.com/gp/product/B07S9QQSH7/
I can't perceive any lag with it, my barometers for it are Art of Fighting 2 and Samurai Shodown 2 both which look great to me on it and I have zero trouble doing any moves and it feels super responsive. I tried it with both the official stick as well as a newer USB stick w/ a Brook adapter.
The down side is it seems inconsistent from game to game. I don't own a lot of AES games but will try what I have this weekend. So far:
Art of Fighting 2 - Great
Samurai Shodown 2 - Great
Sengoku - Some crazy ghosting on the player sprite and some effects. You can remove the usb power and the ghosting goes away, but then it seems to give some odd flickering on the left side of the screen
World Heroes 2 Jet - Great
Two caveats:
Takes from the RGB so depending on your system you might get horrible jailbars on your screen. This would be the case for me but I had cut the traces on my (3-6) board and that took care of it completely.
When you start up the system, there'll be a second or two delay before it gets going, so you'll probably miss the iconic Neo Geo startup
But in general this thing is cool for the low price and the lack of lag to me. I plan on getting an OSSC in the future myself but for now I just got sick of how bad AES composite looks on our TV.
LIfe is so weird, I've had this AES+the games since like the late 90s but it wasn't til recently I got super into fighting games again so I've been playing it constantly lately.