I have minGW gcc installed on my computer from previous projects, and I have recently installed Msys2 so I could develop with GTK. Is it bad to have MinGW and a instance of MinGW on Msys2 installed on the same computer?
The only problem is that it might confuse you. It should not cause any real issues though, because MSYS2 does not add itself to your PATH environment variable, and when you run MSYS2 it will (by default) use a different PATH so you can only run Microsoft programs in C:\Windows and MSYS2 programs. So this means you won't accidentally run the compiler from one environment when you are in a different environment.