Rooting without PC

Pc needed unfortunately. You have to have a pc to unlock the bootloader and then flash recovery. A pc is also needed to perform the s-off procedure if desired. Once those steps are done you don't need pc access anymore.

If a friend or family member has a pc you could use for a little bit to do the above you'd be set

You don't need root to load custom roms but you do need to have bootloader unlocked and custom recovery installed. Pc needed for this.

Unfortunately there's not much you can do with a bit of access to a pc