This scope uses a 35mm tube with a 50mm objective, so you would need 35mm rings in medium or high height to clear the objective bell on a Ruger Precision Rifle, but the exact height needed depends on your rail and mount setup, which is not specified on the product page.
This is indeed a misprint. The Razor-HD 5-20x50 will have matched turrets and reticles, in either MOA or MRAD option!
Anti-Reflection Devices are available for the Razor-HD 5-20x50mm through Tenebraex.
Here is a link: https://armament.com/razor-5-20x50-ard-not-flip-cover-compatible-50vtx0-ard/
To mount the Vortex Razor HD 5-20x50mm Rifle Scope to a Christenson Arms MPR I recommend using the Spuhr 35mm Rifle Scope Mount at the link below. The 30mm high model of the Spuhr 35mm Rifle Scope Mount should work for that set up.
Maximum internal travel of the Razor-HD 5-20x50 is 125MOA!
This it the item number for ring for this scope. VX-RR-PRCN-PMR-35-126
You can choose between the 2 options.
Mounting this on a scar 20 you will need a 35mm cantilever mount.
Provided a sufficiently strong mount, this scope will withstand .308 recoil without issue.
You will need rings that are at least 1.20" tall. Here is a great option under MPN:PMR-35-126 found here:
https://www.opticsplanet.com/vortex-precison-matched-riflescope-rings.html