This is a personal matter, pick what you want, you have to use it. I am a magnification junkie, so a Sightron SIII 8-32X56 sits atop my predator rig. Many, the vast majority, would tell you this is way past overkill for a calling rig.
However, of the 4 yotes I've shot recently, 3 were under 30 yards, 2 were moving, one was killed at about 15 feet trotting away as he saw me when we were about 10 feet apart.
So, the 8 on the low end seems to work just fine for me and the 32 on top was nice for the other at 300.
Figure out what YOU like and what best suits you, buy the best quality you can, we have no business telling you what would be best for you.