Z-axis is one of those "fancy" rifle-type sleeve bearing designs.
 Note the *recommended temperature range" on those.

 Many if not most GPUs see more than 40C at the intake (40C = 104F), which is why ball bearing is the way to go, they're INTENDED for use at higher temps.


 7V out of a molex as LOW currents is fine, just don't try to pull a LOT of current that way - couple amps per PS shouldn't be an issue though.


 I'm not sure if a single molex as used for PC drive/fan connections is specified to handle 80 watts at 12 VDC.
 I suspect it's probably OK though, that's less than 7 amps.