It all depends on the scope you choose for your CZ or Brno rimfire bolt action. The two most preferred scopes for CZ are Leupold and Weaver rimfire scopes. They have the smallest eye piece were you can get away with medium high rings. With Bushnell Elite scopes, you can get away with high rings. Any other scope company you pick, especially Vortex because of their massive eye piece, you must use Extra high rings on a CZ or Brno to get it to clear the eye piece. The Bushnell Elites will work with high rings but just barely.
Example. CZ 455 FS with high leupold 11mm rings and Bushnell Elite 3200 3-9x40. The clearance is uncomfortably close to the eye piece but it does clear.
Put a Leupold 1" tube centerfire scope on there with adjustable parallax and you got a lot of extra room with high rings but you can't get away with mediums. Use a Leupold or Weaver rimfire scope and you can get away with mediums.