you can only use item mods by hex editing unless you have a pc version of skyrim then there are more options

Hex editing is really limited, mostly money and duplicating items. Pc editing, theoretically you can run any command line you could with the console commands, which are pretty extensive if you look at any of the wikis with pretty detailed guides. In practice though some things don't work well, either because some command forms won't carry over in to new saves, won't work, or maybe even crash the game. With patience though (manually moving items is a pain) you can even add or redecorate homes and heavily modify npcs. adding items and character buffs though, as well as fixing quest bugs is pretty easy.

With just a usb you cant mod anything :trollin: