If you go with the Williams mount, you will be able to shoot under due to the over hanging rings. As I said, it is a pretty sturdy setup and if I was going to do a similar rig, that would probably be the way to go. Detachable, but not necessarily necessary.

I just finished a set of rings for a mannlicher that had claw mounts and it was a substantial investment in time, mostly due to the offset. I don't particularly like the offset rear but in this case there really wasn't an option as the bases were already there.
From what I have seen, when working with this type of an action with a split rear bridge, the side mount works best. Go do a google image search on all of the different types of mounts for that style rifle, and the variety is endless.
Mauser, not so much as it is a far easier job.

Also as for the rear sight, I would lose the military one and fit a single standing rear. If you have a drill and a file, not too time consuming a job. Can look very nice and classes up the rifle even further

Cheers
Tom