Apple iPhone/iPad questions?

1 you can use he app called steam link to remote to a computer Steam Link on the App Store (apple.com)

2 you can use the wireless controllers Connect a wireless game controller to your Apple device - Apple Support

3 you can use ms's xbox app to stream

only place you can download apps on ios devices is apples app store

Steam Link lets you stream games from your gaming rig to a mobile device, and it's (finally) coming back to the Apple App Store!

What is a Steam Link?

Initially, Steam Link was a $50 set-top box that you plugged into your TV. This allowed you to stream your Steam library from a host computer on the same network. It came alongside Valve's now-colony Steam Machine initiative.

Considering that most gamers today own mobile devices, smart TVs and strip devices, Valve has discontinued the hardware version in favor of an app-based solution. However, Apple removed Valve Software's Steam Link app in May 2018, citing "business conflicts".

Bottom line, you will be able to connect.