Don’t over complicate it:
Generally, follow MFG recommendations for torque settings.
*I like to put a level on the rifle, then plumb my scope to a plumb Bob 60-100m away, I torque my scope down when my gun is level and the scope has been rotated to plumb.
You don’t have to have a level on the rifle, I personally do not shoot with the rifle canted which I think some people do. Which means if they’re knowledgeable, their rifle is canted to their liking, but the scope is plumb.
I would add a level to the scope, it’s a quick reference that you’re plumb before taking a shot. You simply have your scope torqued down then hold it plumb, set your level and tighten it. But levels on scopes are a controversial topic on the hide so dig around and you can read the counter arguments.. this is what I do though.
Finally it’s worth mentioning, it doesn’t matter if you use a actual plumb Bob deal or something you know is level. I’ve leveled scopes using buildings, I Beams, anything I was relatively certain was plumb with my center line.
Hope this helps there has to be a lot of threads on this topic if you dig around a little.