You can only store one game on the 3-in-1 in NOR ram(the rest is on your slot-1 and you usually load them in PSRAM). I usually don't recommend using just NOR ram because of how long it takes to load a rom (on first run only). Games that have the ability to link into another game (like Pokemon FireRed/LeafGreen) can only do Pokemon Transfers while loaded into NOR, so that's my only exception and/or the game is 32 MB (since PSRAM is 16 MB max)
PSRAM is for people who have pirate syndrome like me where you can't stick to one game and consistently swap through many different games. PSRAM is automatically wiped every time you turn off your DS since it requires power to retain the memory. Good thing it's only used for the rom itself and not the saves
SRAM is automatically backed up into the slot-1 when you boot up your 3-in-1 with a different game (with NDStation, it'll automatically back it up on boot up, but I don't recommend the program cause it's slow and unreliable). Also, using the Restore from SRAM.bin option on Rudolph's/Whatever the new one is called, you can bring in VisualBoy Advance Battery Saves. Just make sure you 1) have the save file properly named in case-sensitive text, and you DO NOT have a SRAM.bin in your GBA/SAVES folder.
If you think about it, you'd never really have to use the NOR RAM ever, since there are so few 32 MB games that are good. There's no real point other than Pokemon, but, I'm not one to play Pokemon, so that's the end of story for me.