I asked a friend about it, and this is what he told me, but there are only a few options to pay with. There used to be amazon gift cards, but its not there anymore:

"If by safe you mean private, then yes, relatively so. There's no public correlation of your fiat spend to your Bitcoin stack. Of course Strike knows you sent money to someone, and that person knows of the trade, but its far safer than a centralized exchange which can be leaked/hacked and tell the whole world of criminals that you have a fat stack of sats and make a good target for home invasion and robbery".