I'm also curious as to the emulation on the drive. I know that NES is scrunched on the screen, but how does it and GB/GBC run on it? Is it consistent and decent emulation? Does saving work properly?
NES/Stretched 16:9 ratio across the entire GBA screen
GB/GBC Half letterboxed 4:3 ratio in the middle of the GBA screen and it's a bit smaller in length to how it runs on the real hardware
SMS/Stretched 16:9 ratio across the entre GBA screen
GG/Can either be kept in its original 4:3 ratio or disable the black bar area to make it pseudo 16:9
Neo Geo Pocket/Hard to tell but I think its the same as the GB screen I never knew the ratio so it may be letterboxed in too
PC Engine/Stretched 16:9 ratio across the entire GBA screen
SNES/Stretched 16:9 ratio across the entire GBA screen, makes so games unplayable due to the unavailability of changing the ratio at will but with time and programming to make a game play like how the GBA would do it... it's indeed possible to make the camera follow the sprite so that the cut off top area can be accessed aside from button holding the select button and pressing either up or down!
As for emulation it depends on your definition of decent, if you want to see how far the emulation pushed the GBA to its limits its quite extraordinary but don't expect it to be perfection like a Raspberry Pi but with what the GBA uses to emulates the games its not that bad.
For example the NES, GG, SMS, GB, GBC runs at a proper 60HZ while the Neo Geo, SNES, PC Engine run at random HZ however some can be sped up in some trickery such as changing the Timer IRQ off on the PC Engine and changing what I presume is the bitrate on the Neo Geo Pocket while the SNES heavily relied on an outdated method of speed hacks that don't function on devices these days to make them.
And lastly as for saving all saved games will be kept on the NES, GG, SMS, GB and GBC as they have a save feature being a save slot, the data is kept in the SAVE folder in the emu save category but be careful on how many save states you make or how many games have been ran on the device as of when it exceeds 11,000 loads it will bring up a Disk I0 error where you would then have to remove all memorized games to get the device to boot up the games again. As for Neo Geo, PC Engine and SNES they don't keep states...
Oh yeah before I forget as of now the PC Engine never worked on a GBA X5 unless you tracked down the pre-made sets that were in a list so there is that too.