theoretically, you could split the files. but idk if the emu's would work with them
I'm guessing not, since the feature that allows Switch homebrew to read split files is a built in feature in HOS and I doubt Android would have the same feature.
You know what I just remembered it's simply not possible to have a file larger than 4 gb on Fat32. You can install a Switch game that's larger than 4 gb through usb or wifi but you can't put a file such as PS2 ISO or Wii ISO larger than 4 gb on Fat32 you'd have to reformat to Exfat. I wouldn't recommend that because Exfat has corruption issues.
Those corruption issues should not exist on Android so if the SD card is used only for Android, it should be safe to use exFAT.
I'm using Android to emulate Wii and PS2.
Convert your Wii games to .wbfs (use Wii Backup Manager), most Wii games in ,wbfs format are less than 4 GB. The ones that are likely to run at a playable speed (as you'll see below) are most probably much smaller than that and should have no issues fitting on FAT32 once converted to .wbfs.
You'll probably quickly realize it's not really worth the trouble to emulate Wii games on Switch. I tried a lot of GC/Wii games on Switch and the results were mostly poor.
GC is hit and miss with many games having audio stuttering but still maybe playable if you don't care about the audio, but there is a decent number of games that run very well with perfect or near perfect audio (once the emulated CPU clock speed is reduced in Dolphin) and are quite enjoyable. So GC emulation can be considered just about good enough to be worth bothering with. Personally, just having Paper Mario TTYD running at 1.5x native res at good speed made setting up Switchroot Android to screw around with Dolphin worth it for me, but it's getting an official remake now so that's kind of moot.
Wii games on the other hand are a different story, the Switch is barely able to do GC which means there is no way most Wii games are going to run well since the Wii is about 50% more powerful. Out of all the games I tried the only one that I would consider playable and enjoyable was Super Paper Mario. Everything else just ran far too slow. That's a pretty small game (only a few hundred megs IIRC), and it makes sense it would be less demanding considering the 2D/2.5D graphics. Based on my tests, any full 3D Wii game is probably going to run badly, you are mainly limited to 2D games and some 2.5D games.
You might think based on that that New Super Mario Bros. Wii would work well, but IIRC it was one of the poorer performing games.
I never tried PS2 on the Switch, AFAIK it is more demanding than Wii games in Dolphin so high chance only the most simple 2D games would run at good speed, if even that.
I totally get just playing around with emulators and trying games out for fun even if you don't expect them to be playable. But it's probably not worth jumping through hoops to get > 4 GB Wii and PS2 rips to work, when even smaller/simpler games struggle. There are plenty of < 4 GB games for both Wii and PS2 to try out. Bigger games are logically less likely to run well since they are more likely to be the ones pushing the limits of the platform.