You can very well mount the cv with actuator in horizontal position.
Care to be taken for the following:
1. actuator vent should not face aerial direction
this is to prevent rain water getting inside the actuator
We have faced a typical problem with shutoff valves mounted in vertical lines,i.e intially they work fine but over a period the torque required goes up and hence the actuator starts failing. The same if installed horizontally works fine.This type of condition existed for three of our valves in our plant. These valves were replaced with new ones, but the perfomance was the same.
So you are requested to avoid mounting the valves in vertical line.
Depends on the valve. If it's a sanitary rated valve, it may need to be mounted in a certain orientation to drain properly according to sanitation requirements.