FlappyFalco : CFW does not always mean redNAND.
Users are not installing games "on CFW".
CFW is only a state of the console with some patches, it can be sysNAND with patches, not necessarily a different location (like redNAND).
so, saying "installed games on CFW are also on sysNAND" is like saying "installed games on sysNAND are also on sysNAND". that's exactly the same thing.
Another note, CFW does not necessarily require a "delete", just rebooting the console is enough.
it depends the user's way of launching CFW and patching the console.
if the user is using browser hax to run Simple signature Patcher, then there's nothing installed permanently on the console, and therefore nothing to delete.
Maybe if Argentlan is worried about installing, uninstalling and leaving trace of a CFW, he can do all this temporarily with browser hax and homebrew launcher, instead of installing a persistent solution like haxchi or CHBC.
I can only install virtual console games if I have CFW right?
can I remove CFW if I change my mind in future?
and there is some disadvantage about installing a CFW? is it worth?
you can only install virtual console games with a patched firmware, because VC games are tied to a specific console so you need to patch your console's function use to check the consoleID to allow installation of someone else's game dump on your console.
this is not necessary for Disc based games, only eShop based games and DLC.
like said above your quote, you don't even need to install any CFW, you can just patch the signature check function temporarilly before installing or launching a game tied to another console.
Disadvantage about installing a CFW? if you follow the instructions, none. if not, you can damage your console.
disadvantage about NOT installing a CFW : you have to run a signature patcher manually each time you need it.
to uninstall a game, go to data management.