Right to the point: don't use batocera because the one guy doing it stopped and said use his other thing koriki. Unfortunately for all cfw for the rg35xx none of the developers have released the code they are legally obligated to release, but what can you do...
I have the rg35xx and use garlic. The fake sleep mode works well. Instant off and then it takes maybe 10ish seconds to turn back on. It definitely is fast enough that I don't mind turning it off even when I know I'll be turning back on in only a few minutes.
I haven't had a game crash on me but the automatic save states have not loaded a couple times so make sure to make your own.
I haven't used koriki because garlic does most everything I want. If anyone releases their source I might test that because I want to do some link cable emulation stuff, but none of that exists currently.