Some are for sure. You can tell if there is any ‘buy bonus’ buttons visible or not.
Big wins page can be a bit misleading though for sure. As you don’t know if its a bonus buy or spun in. It can look like a huge max win, but really its only a 25x (retro tapes buys)
Buys don’t pay any better or wager any better than spins, and I wouldn’t say the slots play/pay any better offshore as someone whose done both.