I’ve been playing with the Steam Link app for Android (Google Nexus 5X) with a Xbox One X controller (with Bluetooth). The benefit is I can play while the tv is in use (the PC is connected to the tv) or in bed.
By default the triggers were reversed, but it was easy to check and correct all the mapping through the app. The app recognizes that I am using an Xbox One controller.
The PC needs to be awake and unlocked and have Steam running.
The device with the app needs to be on the same network as the PC. My PC is connected by ethernet and phone is connected by 5GHz to the router. I have read that someone was able to use the app offsite through VPN.
The PC is doing its normal work of making the game run, so the PC can’t be in use for other purposes. The game will be running with no sound on the PC.
While playing on the app, someone can still provide inputs on the PC. Between the 2, the app is dominant and can interrupt the PC inputs.
The app has a filter to only show games with controller support. Games that don’t show controller support may or may not work with the app.
Black Flag worked after sitting at the PC while the Ubisoft launcher wanted an update.
Dark Souls Remastered works. I had a streaming hiccup where the screen was out of sync for about 10 seconds but luckily I was in a safe area so I just waited it out. Also, I moved from the same room as the router to far away and streaming was jumpy while moving but then settled down.
Dead Space 3 (EA Origin as a Steam shortcut) did work.
Friday the 13th works.
Killer Instinct works.
Metal Gear Solid Phantom Pain works. Back is used to bring up the Steam overlay, so to push back in game requires pushing back + B.
Need for Speed Hot Pursuit  checks for an awake controller on the PC, so it doesn’t work with the app.
Resident Evil Remastered works with some issues. The developers didn’t hide the mouse cursor so I had to use my PC mouse to push it off to the side. The game also stops responding on exit and I couldn’t get around that in the app.
I could feel slight input lag, but not enough that it really bothered me.
I plan to get one of these to attach my phone to my controller. https://www.amazon.com/gp/product/B01MS ... ELH8&psc=1
I thought about getting this instead. https://www.amazon.com/gp/product/B01KZ ... WM4V&psc=1