Just google, for example, "voodoo 3dfx iso" (in the case of voodoo driver) and you will find some drivers in ISO format that you can use in your emulated CD drive, than just follow the install in Win98. If you just find the drivers in .exe you can save them as ISO using any program like "IsoCreator" and use them in your emulated CD drive as well...maybe the hard part is to find a proper driver, in the case of Win98 any S3 based video card will work as a basic driver to start
As for the joystick I selected "CH Flightstick Pro" in joystick config under PCem and in "Joystick 1" "device" I just selected my SAITEK (it was seen automagically by PCem) the pain was to map correctly the buttons inside the emulated Win98..a lot of try and errors...
I know its hard to set PCem correctly, but once done you will have a good time installing and playing old games...lol