The low latency versions still output only 320 gameboy lines in 480p. GBI ull resizes the output to around 524×320 so it doesn’t look good with any samplerate including 866. ll version outputs 480×320 in 1:1 mode and looks good with 858 samplerate in 480p.
With the regular version you can set aspect to 3:2 and zoom 3x to make it fullscreen but if your display has overscan on 480p then parts of the screen will be cut off. It also has more latency and uses frame interpolation so scrolling is blurry sometimes.
The best for me is still GBI ll on 1:1 on 240p lineX5. Thanks Harrumph for the optimized settings.