Anything portable has always emulated well (or at least have since 2012).
Virtual buttons exist for the gamepads of older devices (NES-derived layouts generally look pretty good, so NES/SNES/GB/GBC/GBA emulates well).
The 3D home consoles tend to be a bit more dependent on the game (early 3D games have some pretty shitty button mappings in general and that's only amplified when emulating with virtual buttons).
As for emulation quality; handhelds emulate really well. Consoles made after 2000 are a bit of a toss-up at times, but generally also work decent.
As for battery drain; not an issue with handheld/old system emulation. Can't speak to home console emulation sorry.
Virtual buttons exist for the gamepads of older devices (NES-derived layouts generally look pretty good, so NES/SNES/GB/GBC/GBA emulates well).
The 3D home consoles tend to be a bit more dependent on the game (early 3D games have some pretty shitty button mappings in general and that's only amplified when emulating with virtual buttons).
As for emulation quality; handhelds emulate really well. Consoles made after 2000 are a bit of a toss-up at times, but generally also work decent.
As for battery drain; not an issue with handheld/old system emulation. Can't speak to home console emulation sorry.