Thank you very much!
If you'd like to watch my playthrough of it, here's the VOD https://www.twitch.tv/videos/2263555539?t=2h58m12s
Starts at about 2:55:00
I must admit, kinda laughing a bit at your guesses as to why it's lagging lol
It lags because it's a real Game Boy game, and GB Studio's platformer engine is a little too much for the good ol' GB CPU to handle...
But the GBC CPU has double the clock speed than the original GB one, and I'm working on a colour version right now and well... Literally just ticking the colour box and doing nothing else has already eliminated the lag!
Frankly, the only reason why I didn't do it to begin with is because this is the GB Jam, not the GBC Jam xD