Anyone here use snaplii for gift card cashback? is it actually legit?

I saw someone mention snaplii on here a while back saying you get cashback instantly when you buy gift cards through it. like right away, not pending for weeks, does the cashback really show up right away? and is it actual cash you can withdraw or is it locked into buying more gift cards

Also which stores do you guys mainly use it for? i do most of my spending at walmart and costco so if those arent on there its kinda pointless for me. and does it stack with credit card rewards or does buying a gift card mess that up somehow.