Forza Horizon 3 can be bought for Windows10 from Official Windows Store now.
But could I run it on PC even if I buy USED physical copy for xBox one?
I only buy from Steam, but there must be better options right? (I am from Prague btw).
Guy, this is KC:D forum… 
But I think your idea of buying for XBOX ONE and running on PC
works: http://www.xbox.com/cs-CZ/windows-10 .
In amazon PC games get cheaper.
See you.