Hi, I think that I might answer your questions, if something is unclear, feel free to mention it!
-I don't know what "SPS" is but if you install games using any title installer (ex: Tinfoil, Goldleaf, Awoo...) the chances that you get banned are really high if you don't turn wifi off and basically, Nintendo can easily detect that you installed those game so yes, you could go online with those in theory, but by doing so you're almost guaranteed to get banned. So the only way to go safely online on a game is to actually download it from the e-shop/use its cartridge on your "clean" OFW SysNand
-On switch I don't have any experiences with non-Nintendo consoles but as far as I know, GameCube emulation with Lakka is good with some overclocking, it can run a fairly good amount of games. I searched a bit on YouTube and the switch seems capable to run PS1 games at full speed as well as psp. I don't think you'll have any luck with wii games tho.
-If you have a legally obtained game on your switch you can play it however you want, OFW, CFW SysNand, CFW EmuNAND it doesn't matter at all.
-If you install a game that you pirated, if you don't take "precautions" (that'll explain below), you're basically fucked, it's really easy to get banned, in fact just running CFW can get you banned.
So now that I answered your questions, let me give you a few suggestions since you're totally new to the hacking scene, first of all your "NAND OS" doesn't mean anything, there's one and only one NAND to your Switch whether your run or not CFW (custom firmware). Your OFW (Official Firmware) is your "OS", basically your switch is running multiple "OS" when installing CFW/EmuNAND.
Before doing anything I HIGHLY recommend you to make a back up of your NAND in case something goes wrong and be precautious, don't download everything, always verify what you're doing... You can get banned just by entering CFW with internet connection (without blocking connection to Nintendo's servers using a DNS). Also there's no "restriction" for running a game, you can run ANY switch game on CFW (meaning that there's no game that won't play because you use EmuNAND or SYSNAND CFW). I highly recommend you to enter the fewest times possible SYSNAND CFW because it's the thing that is the most probable to get you banned so every time you enter it, make sure you're on airplane mode (for EmuNAND, just use Incognito+90DNS or any other DNS that's blocking connection to Nintendo's servers). Have a good time with CFW!
