Which files do I copy to transfer Flight Simulator 2020 to another PC?

Here is the thing laptops are underpowered thars why you are facing performance issues

A gpu on a laptop isnt the same as a desktop you need to up the specs to do the same thing a desktop does

Do you have a clear way to do it? I bought it from steam

It can be a lot easier, if you downloaded it from MS store, open your settings app on the win 10 pc, select the app from the list of apps you wish to move, in this case MS Flight sim, select move and move it to the drive you want it on. Wait until move
is complete and validated. Thanks to old guy geek video on you tube, credit were its due. No harm to have a look at his video on YouTube and subscribe,

I got mine from Steam and still figure out how to backup the files of the entire game...

Steam backup only the part downloaded from them... Like 5xxMB that's it

because FS2020 uses a launcher that also downloads and installs then the file move can be done, all other games cannot be done like this.

Nice one for sharing this though.