I’ve only just seen this.
Are you increasing the graphics up to 1080p, 4K etc in the emulators? Dolphin will hammer a lesser card for upscaling graphic definition (GC was 480 native and Wii was 720 native). I have a GTX 960 in mine and it handles everything fine in 1080p/4K. I’ve even added RPCS3 running PS3 games comfortably but it takes some grunt to handle it.
I use retroarch for everything from NES/SMS up to and including PS1, the PS1 games can be upscaled to HD with the beetle HW core. It has a decent PSP core as well.
PCSX2 for PS2 - again the graphics can be increased comfortably.
Dolphin for GC and Wii, I use a ‘dolphin bar’ to use the wiimotes for Wii and a USB ‘smash bros. 4 port GC controller adapter’ to use the original GC controllers which have analog shoulder buttons (essential for certain games on the GC)
Cemu for Wii U - although I have a hacked Wii U that runs GC/Wii/Wii U without emulation via ‘Haxchi’, which I’ve had for a few years.
There’s even a Switch emulator in its infancy called ‘Yuzu’ which is already coming on leaps and bounds.