Can Xbox players join PC players in multiplayer? Do I have a choice?
Yes. "Gamers on Xbox One and Windows 10 can now play select multiplayer games together. Gears of War 4, Forza Horizon 3, and Sea of Thieves all support cross-play between Xbox One and Windows 10 PC. If for whatever reason you don't want to play online with PC players, or with Xbox One players, you will have the option to filter matchmaking by platform, but of course we encourage everyone to have fun with the game with as many players as possible in Horizon 3 via Cross Play."
Do I need Xbox Live Gold for either Xbox or PC? Can I play offline?
Gold is required for console multiplayer features. "You don't need a Gold subscription to play any of the online modes on a PC.
Official page and FAQ: http://www.xbox.com/en-US/games/xbox-play-anywhere
Xbox Wire video tutorial: http://news.xbox.com/2016/09/15/everything-you-need-to-know-about-xbox-play-anywhere/
How does Xbox Play Anywhere work?
When you buy an Xbox Play Anywhere digital game through the Xbox Store or the Windows Store [or via a digital code at participating retailers], it’s yours to play on both Xbox One and Windows 10 PC at no additional cost. To take advantage of Xbox Play Anywhere, you will need to have installed the Windows 10 Anniversary Edition update on your PC, as well as the latest update on your Xbox One console. Then, simply log into your Xbox Live/Microsoft account and your Xbox Play Anywhere games will be available to download.
Does Xbox Play Anywhere cost extra?
No, there is no additional cost for Xbox Play Anywhere. When you buy an Xbox Play Anywhere digital game, the ability to play on both Xbox One and Windows 10 PC is included at no additional charge.
Can I be signed into the same game on Xbox One and my Windows 10 PC?
At any single point in time, you may only sign into the game on one Xbox One console or one Windows 10 PC. You cannot be signed into the same game on both an Xbox One console and a Windows 10 PC at the same time.
Will my game progress be saved on both Xbox One and Windows 10 PCs?
Yes. When you play an Xbox Play Anywhere game, your game progress is saved on Xbox Live. So, you can pick up where you left off on another Xbox One or Windows 10 PC, bringing all your saves, game add-ons, and achievements with you.
Will downloadable content for Xbox Play Anywhere games also be playable on both Xbox One and Windows 10 PC?
Yes. Downloadable content that you buy or earn for an Xbox Play Anywhere game that you own will also be playable on both Xbox One and Windows 10 PC. This includes game add-ons, Season Passes, consumables and in-game unlocks.
Will I earn Gamerscore and Achievements twice if I play the game on both Xbox One and Windows 10 PC?
A single shared set of Gamerscore and Achievements will be earned and awarded for Xbox Play Anywhere games.
(Forum Q:) Can I give away my Play Anywhere PC copy or let others use it while I use the Xbox version?
No, the PC version is tied to your purchasing account, and can only be logged in one place at one time. See Xbox Support
(Written by Manteomax)