1. I'm surprised Game & Watch games are working at all since our MAME core is Arcade only. Also very odd they only work with Open Advanced, you are actually on the latest BizHawk version, correct? The core is deciding the aspect ratio here too so I would assume it would be actually correct.
2. You are not supposed to load with the .bin file, you are supposed to load with the .cue file. The .cue file tells the emulator where the .bin file is, possibly where other .bin files are at, and how the .bin file is structured with its tracks and whatever CD modes are used. This is the standard across emulators dealing with cue/bin, at best an emulator might be "smart" and use the .cue file next to the bin (although the .cue files are supposed to contain a file path to the .bin, so this is kind of wrong regardless) or maybe generate some .cue file to use with the .bin (which is rife with potential issues since it has to make assumptions about the .bin file that could very well be wrong). Not sure what you mean by the "aspect ratio is off," the aspect ratio presented with default settings would be given using the core's numbers, which would have the correct PAR and such.
3. C64Hawk isn't perfect, although using T64 isn't giving you any favors, as that's an incomplete format (we don't actually support .t64 in the core; you should be using .tap files rather):
https://github.com/TASEmulators/BizHawk/issues/1501
Not sure why .CRT would give any particular issues (it's just a cartridge), perhaps just some other compatibility woes with C64Hawk here.
VICE port is already a request:
https://github.com/TASEmulators/BizHawk/issues/2002
4. Libretro has "experimental" slapped on for a reason: it's nothing more than a curiosity to use them in BizHawk. Some cores don't work due to us not implementing all of libretro's bells and whistles and some don't work due to relying on unspecified behavior with RetroArch.