Airbus A320 automatic speed mode protection in SRS vertical mode
High speed protection is still available (in normal law) in SRS (check FCOM DSC 27 20-10-20). 

What you will not have is the reversion mode of the autothrust to Speed. You will get the protection  (THS freeze, spiral stability to 0deg, max 40 deg bank, nose up order) but thrust will remain in THR CLB.

I suspect the reasoning was that SRS mode implies you are pretty low on altitude, and you do not desire an automatic (and uncommanded) reduction of thrust on, say, a windshear.

Of course, in this particular case the high speed prot will activate at VMO/MMO so if you manage to get that fast while still in SRS you have bigger problems than the thrust

For your second question: mode reversion to Speed will occur at VMAX (which is lower of VMO, VLE or VFE), but for SRS there is no flap overspeed protection so only VMO will trigger it