question

• There's no documentation about the real money currency being used by Playfab. Is it USD or what?

PlayFab itself does not offer the payment processing feature, however, it supports IAP (The "RM" (Real Money) VC type is reserved for real money purchases ) and Non-receipt payment processing, players can use any currency specific to their countries/regions to purchase items from PlayFab. Please check out these docs:

Getting started with PlayFab, Unity IAP, and Android

Non-receipt payment processing

• Does Playfab provide the payment processing API? Or do we have to purchase some plugin and integrate it?

As stated above, PlayFab itself does not offer payment processing, it’s only used with other payment providers to verify purchases and therefore grant specific items for the players.

• If Playfab does not provide payment processing, what is the work around and what plugins will you recommend?

As mentioned in this doc: Non-receipt payment processing, for Non-receipt payment processing, we support Facebook, PayPal, Xsolla, and Steam.

For IAP, we support IOS & Android purchases.

• Can we make refunds? And if the refund is made how to take the item back from Player?

You can make refunds on whatever the payment platform you’re using and use RevokeInventoryItems/RevokeInventoryItem to revoke items for the player.

• Can I show custom store to each player based on their game performance/level?

Yes, PlayFab offers Custom stores for player segments, which can be used to show custom store to each player based on their game performance/level, please navigate to the link to learn more.