Its basically like any remote viewer; RDP, TeamViewer etc. but their video is waaaaay better. It plays really well, dependant of course on your net + hardware, as you are effectively streaming your game to your buddies.
I have a 2 year old laptop and fibre and its nearly perfect. There isn't any configuration, you both have Parsec loaded. You host your game and invite your buddy (lots of different ways to do it) then when they connect you give them shared access to keyboard and mouse (click 2 icons) and you're done.
Parsec is pretty impressive for a number of things, including remote working. They were just bought by Unity.
You're describing a system that doesn't have a lot of gaming punch, OP.
Make sure you're totally disabling shadows (that was my biggest resource hitter IME).
Also, if you can't get this running well on your laptop, you might want to try it using the freebie version of GeForce Now, Solasta is listed as a supported title.
Yes, you can play it on your phone if you use Steam Link which I use a lot when I just want to lay down on my bed and play video games that don't require much of reaction time. It is totally free and it is an official Steam app.
To set it up, you need to install the game on your PC/Laptop and link your device to your phone. After that the game you want to play might not appear on your library first. You can either click on and off Browse > Games until the game you want to play appears. Or you can just manually launch it through your laptop/PC.
Once you launch the game there are a lot of ways you can control the game with. Choose whatever feels right to you and customize it to your own comfort.
Note, both your phone and your machine should be on the same wifi. I think that's not necessarily but that's easier to do.
Click here to view the official Steam Link app for android .
Take care and good luck. If you have any further questions I'm have to answer them. This method is not perfect but it works just fine and I love it.