I agree the level-level-level bubbles are not much good. It is hard to find surfaces that they will be verifiably level on
turrets could be off from the factory, action rails could be a little off and the bubbles may not be level.
I use this tool, the EXD ENGINEERING : EXD ENGINEERING VERTICAL RETICLE INSTRUMENT - World's Largest Supplier of Firearm Accessories, Gun Parts and Gunsmithing Tools
which you put on the scope barrel and rifle barrel
to align them while you have your gun in a vise, when the bubble is level the rifle is UNCANTED. Then rotate your scope to align the reticles with a distant vertical or horizontal object and lock it down. I use a 4' level on a fence out the door about 30 yds out.
As far as alignment of the bases and rings, I have a 1" and 30mm Wheeler Engineering Scope Ring Alignment and Lapping Combo Kit 1" and 30mm - MidwayUSA
which are very useful when you mount dovetail rings or the rings with the windage adjustment screws. For the more fixed type like Weavers or Talleys they will only tell you if you have a problem, then you could lap the rings or order offset rings for misaligned base screw holes.
I have found the EXD indispensable for scope mounting and usually put an anti-cant device on the scope at the time I am aligning the scope and barrel and leveling the reticle. If I ever move the scope it is easy to just level the scope to the anti-cant device. It is also helpfull for long range shooting.