Discussion Options to implement accounts, currency, IAP, unlocks

I'm building an online game using Photon Networking's Fusion plugin. It's supposed to be a match based game where you earn in game currency, XP, unlocks new parts etc. I'm looking for a way to do all of this neatly in the cloud, i.e. the player logs into an account gets secured data. Currently the game runs peer to peer, so hosting dedicated servers is another future headache

I'm not sure what are the best and most approachable options to implement account data, in particular in-game currency.

Currently the game is on closed beta on Steam, so I could perhaps just use steam integration to get usernames and cloud saves to sync data. In that way the progress data will just be stored in files you have offline, which makes things simple, but perhaps too vulnerable to be hacked? I don't think Steam offers in-app-purchasing services either but I could be mistaken.

I was also looking at Unity gaming services, which seems to offer all these things at a price, but then again do players have to make a Unity account to log into the game? Is it the best way to do in-app-purchases? Do they take a cut?

I think you can guess I'm kind of lost and don't really know where to start, any info is welcome.