Sure they are !
I RFQed a rolled ballscrew from HiWin it was C7 grade, it had a max backlash of 0.001mm & +/-50µm per 300mm variation.
If there's 1mm or 0.5mm of space between the copper traces on your pcb, C7 is more than enough.
C0 to C5 grades are a lot more expensive...to me they're overkill/overpriced.
You should use the 7200 series bearings, you'll need TWO identical 7200 series bearings, mounted back to back, in order to make ONE fixed end support for one screw.
Also take a look at post#1 in the ballscrew basics thread for more info & schematics of bearing mounting.
Your price seems to be good, so please give us a link to the chinease ballscrew website, i'm interested to see their specs.