I plan to do a pc upgrade very soon. Alongside that I plan to start with Mint or Fedora. Is there any real or big downsides to dual booting ? Aside from the harddrive space lost ?
If I like or really like my time with Mint I would probably switch permanently but I felt like I wanted to test it for a couple of months before making a complete switch.
Im a big 
so that impacts my consideration. Dont really play much multiplayer shooters so I dont have a problem with kernel anticheat games not working.
In theory sure I have a strong feeling you’ll just acquire 20 more headaches and with secureboot anticheat and whispering of tpm 2.0 requirements for anticheat the headaches wont really even solve the problem.
I’ve used linux for about 15 years now and i dont think ive ever experienced a stable dual boot ever that didnt require me to fix grub in some way. The order also matters you install windows first and linux second the other way round will disappear the grub bootloader lel. And with gpt and uefi bios the headaches grow.
Personally im waiting for the industry to change its mind it causes less problems