Xbox PC App Question

So I thought of something earlier today and I wasn't sure if it was possible, I tried searching online for the answer and it kept taking me to the support page of Xbox. I got myself a gaming PC, a pretty decent one that I've been gaming on for the past few years; while making upgrades throughout the years to keep up with current games. A few months back, I got myself an Xbox One S as a gift. Been wanting to take a break from PC gaming and go back to consoles, mainly because most of my close friends play on the Xbox One.

I know more titles are implementing the cross-play feature from Xbox, you have the buy a copy for the Xbox and get a copy for PC, and pretty much that whole connecting Windows with Xbox; unifying both platforms. My question is this, when I log onto the Xbox PC App, I notice I can add games, now I'm wondering, I know I can purchase Quantum Break and Gears of War 4 for instance off the Windows Store and it'll load it straight to the Xbox PC App correct? But if I purchase for instance, Quantum Break on Steam, it'll play through Steam and not function at all with the Xbox PC App correct?

What I'm trying to do is, I own Rainbow Six Siege, Quantum Break, Watch Dogs 2, & Forza Horizon III on the Xbox One, could I somehow load these games onto the Xbox PC App and play them on my PC directly from the Xbox PC App? And still be able to join parties, earn achievements and such?

I'm hoping this isn't too confusing to understand what I'm trying to explain...sounds confusing in my head...lmao

@kinky-unikorn: "But if I purchase for instance, Quantum Break on Steam, it'll play through Steam and not function at all with the Xbox PC App correct?"

Yes, only through steam.

What I'm trying to do is, I own Rainbow Six Siege, Quantum Break, Watch Dogs 2, & Forza Horizon III on the Xbox One, could I somehow load these games onto the Xbox PC App and play them on my PC directly from the Xbox PC App? And still be able to join parties, earn achievements and such?

If its the digital version of those games, yes some are cross-play, if its the disk, nope.

Mmmm I only own physical copies of my games for the Xbox, I'm not a fan of digital on the Xbox. So pretty much, if the game is available on the Windows Store, then it's possible to play it on the Xbox PC App, and earn achievements, etc. If it is not, then I couldn't link a game from Steam or Origin and add it onto the Xbox PC App and start playing and earning achievements?

What about this streaming feature I see that the Xbox has for the PC?

Yes to the first question, you cant link the games.

Just buy digital games on your PC through the Xbox App, then you will get the game twice for 1 price. Just make sure its cross-play and cross-buy.

No idea about the streaming.

Mmmm alright bro, so for me, it's not technically ready for what I was exactly looking for...lol. Thanks for your help though!