SRAM and PSRAM are not the same. SRAM is the battery backed RAM that stores your saves regardless of where you stored the game. PSRAM is the volatile RAM your write games that need to be rewritten to the cart when it is w/o power. It's also the extra RAM Opera and homebrew uses. NOR is the non-volatile flash that you write games to that do not need to be rewritten after you power down.
I'm not sure how Wood handles the EZ 3-in-1 but if it functions like most other offerings it should automatically back up your save from SRAM any time you start a different GBA game or write something new to the 3-in-1. It doesn't matter if you burned to the game to the NOR or wrote it to the PSRAM, the save is still saved in the SRAM and should still be backed up when it needs to be over written for a different games save.
The reason I mention NOR not being backed up is only because you can use the 3-in-1 as a stand alone cart if a game is burned to the NOR. If you boot the 3-in-1 in w/o using a slot-1 cart's menu or ExpLoader or the like (e.g from the DS menu or in a GBA), even if you have a slot-1 cart in your DS it will not back up your save to SD. Of course, you need a slot-1 cart to burn/write anything new to the 3-in-1 and it will back up the save the next time you change games from your slot-1 so your save would be just as safe. You would however need to make sure your save was backed up to SD by booting a different game before storing the save on your PC.
If the battery dies then your saves will be lost as soon as you power down the DS. Since the back-up to SD happens before you run a game from the 3-in-1 (in the instances I've discussed that it does), you will not be able to save from session to session.
Don't fret about the battery too much, in my experience the premature deaths that people keep talking about are exagerated.
