I’m considering the 1x micro prism acss cyclops for ar 15 chambered in 6.8 spc
Are the holdovers compatible with 6.8?

As for a magnifier, do I need the Pegasus even though the micro prism has the range  measuring etched in?

Use Strelok or Chairgun or another App to test the reticle with your rifle and zero.

No BDC will be a perfect line up with more than one or two setups. However, almost any BDC can be made close to any setup by playing with zero distance and small modifications to zero like an inch or two high at 100y.

You do not need the Pegasus for a Microprism.

Personally I tried a magnifier with a cyclops years ago and it didn’t work for me at all. I had to drastically change my diopter setting on the optic to get the image remotely clear.

Wow ok
I wonder if it was Becuase the diopter was turned too much one way or the other?
Interesting.