Do some of the creators of those super detailed head textures use touch pens or do they just use their mouse?

most of the artists use tablets for smoother lines and stuff, such as jebus. But others use the mouse and still do some pretty dope shit, such as krisis13.
There's also lazy nezumi pro, which really smoothes the lines with the mouse

iawesome uses a trackpad but he mostly uses selection tool combined with brush to get smooth lines.
it depends on what tools youre more well equipped with, if you're better with brush/ pencil and blue etc. go with touch pen.
if you know how to use the pen tool and selection tools then you dont really need a touch pen at all but you're pretty limited.

just a heads up you might need to mess around with a few settings until you get a good configuration for your drawing tablet.

i have a tablet but mouse works best for me

They use iPad app call drool my thong! But also ipad 2

mouse works best for me tbh

I personally use trackpad a lot. I'm on a Mac so I have the three-finger-drag option enabled. People tell me it's fucking weird and that I should seriously consider using my tablet once in a while but I've grown attached to my trackpad.

Bear in mind though, I've used my trackpad to create art for nearly 2 years. Think twice before getting a tablet. If you aren't planning to pursue an art career, it's probably not worth it.

lolRedPanda ninja'd me?

Sai has a smooth line tool, and I believe there's a PS addon that does the same.

i'm sure you mean a tablet, and yeah, most good textures are made with tablets because
it's kinda easier than with a mouse, but if you're good with a mouse (or trackpad), then
us it instead.. It helps to try a tool which you aren't acquainted to, but it's not necessary
for texture making.