I took some time to calculate and dial in the optimized settings for GBI (GBI-LL with 11:10 PAR and 1:1 PAR, and GBI-ULL).
Google sheet here
I don’t have any GameBoy games, so this was all done for GameBoy Advance. In my opinion, for GBI-LL the results were best using the 1:1 pixel ratio. Using the default 11:10 resulted in some slight kind of ringing effect.
As a side effect, I now noticed that my Bandridge automatic switch does in fact cause some horizontal “smear” (I’ll post in one of the shmups threads about this). I had not noticed it at all before when using generic modes, and optimized mode for my SNES was blurry anyway since I have a 2-chip. Going straight into the OSSC gave perfect result, looks pretty awesome tbh, even when scaled to full screen. I’ll see if I can add some pics tomorrow.