You might try
Magisk - if it works on your phone, you get root. (It's a systemless root, so the same file works on all phones it works on, you don't have to wait for someone to find an exploit for your phone.) Since you have the bootloader unlocked, and that's the way Magisk is installed (using TWRP), it may work. (Install TWRP first - you'll have to see if there's a version for your phone. If there isn't, you may have to install Magisk the recovery "install from SD card" way. But it's a GitHub project, and the developer, Topjohnwu is available on XDA, so there's help available.)
Make sure you have everything backed up, and a copy of the stock ROM, just in case.
And, as Mooncatt said, to run a PC game (that's code for an x86 or x64 CPU), you need a PC emulator, and everything runs very slowly on any Android PC emulator (they're all built on QEMM - which crawls). Even a Windows phone, using an X86 CPU, doesn't run PC games or, at best, runs them so slowly you might as well not bother.