I have one of those exact HD converters and my TV happens to be fussy and won’t accept most modes from the OSSC. This makes it work, but I noticed I get a bit of frameskip at least on the Genesis. Every 13 seconds I see the same frame twice. I assume this is because the Genesis is 59.91Hz but the device only puts out 60Hz (or 59.94Hz likely)
I also have it much worse with the PS1 where it gives a frameskip once every 2 seconds for a few frames then goes 4 seconds before repeating the cycle. This is a PAL PS1 though and a 240p game (49.79Hz).
I assume the consoles that run at the exact 59.94Hz will have absolutely zero issues and likely if it’s being used for capturing, the framerate is probably already halved anyway, meaning it will be unnoticeable. For how much of a cheap solution it is, 1 lag every 13 seconds for recording wouldn’t even be noticeable anyway unless you’re running a scrolling test.
Anything that runs at 59.94Hz though even works perfectly on my TV and doesn’t have much added input lag (it’s so slight you wouldn’t notice it in most games). Running SCART through the scaler however results in about 5 frames of lag which is kind of expected for a device like this.
With the OSSC first then using the scalers HDMI though as people are suggesting, it feels like it’s literally only about a frame to me, if even that much.
If you could adjust the timings very slightly on the scaler, it would literally be a cheap 100% solution for TV’s that won’t do over line2x.