Hello,
For your question related to speed computations, all effects are taken into account in order to yield the most accurate TAS possible.
The computer in question will rather be the ADC (the name can vary depending on the aircraft model)
At higher mach numbers, your max coefficient of lift will decrease. As well as your stall angle, by the way (alpha prot and alpha max decrease dramatically).
Hence, your VLS will increase accordingly, in EAS.
The CAS increasing above the EAS will moreover increase the VLS value read in CAS.
Yes, since your PFD indicates a CAS (the PFD indicates a IAS by definition of the word indicated, but the speed that is shown is actually correct so it's also the best estimate of the theoretical CAS), it will be a different value than the EAS.