I'm getting a better understanding of this now.
I happened to find this basic cobra inverter that's so cheap and simple with alligator clips included that I'm thinking about getting that instead of the pure dc usb setup (which seems enticing exactly perfect for my situation cost and use). But every now and again I might want to use normal 110 minimally, such as hair cut or coffee grinder.
https://www.ebay.com/itm/114099426000
Is there something that says "stay away" that I can't see other than the really low 20$ price?
And I don't know if it's me not knowing exactly what to type in but I really couldn't find normal 6v golf cart batteries online that wasn't in a bundle or priced really weird but I found this affordable battery from auto zone. Would this work fine? It's <100$
Battery from autozon