I have always used this site as a guide:
http://www.mil-rad.com/scope_ring_calculator
They have your scope in there with predefined measurements, which is great because as another user said, you can’t just use 50mm as the bell measurement. It also reminds you not to forget scope caps! Vortex defenders eat that open space up quickly!
But the person who suggested waiting until you have the scope and using pennies or something similar has the best idea. I actually just used printer paper last time I did it.
Depends on what you are looking for. Are you looking so that you can have the scope as close to the barrel as possible or best height for your setup? I tried the whole (it must be as close as possible thing for a while) and then realized how much more comfortable and therefore fun shooting can be when I ditched that idea and went with what is comfortable. This is especially important when you don’t have an adjustable cheek rest. With no adjustable cheek rest, I always suggest testing first.
With only a 50mm bell, you can get by with low-medium rings as you said (words depend on the manufacturer). My go to height is usually 1.1” but you are probably ok going a touch lower at 1”. Again, I would test with your scope and your setup. On second thought, that 30moa might not fit that low...
Get that right first and then worry about the manufacturer and style. I personally like higher rings, allowing me to set up more vertically. Depends on how you are shooting though.