The nose to charging handle is to maintain a repeatable, consistent checkweld and sight picture. Some don't use it, and are able to maintain consistency.
Badger TAC latches (or the like) help charging a scope mounted weapon. Another avenue is to use a side-charging upper.
The cantilevered scope mounts are primarily used to move the scope as far forward due to eye relief. Larue makes the best quick detach (QD) cantilever mount... also one of the most expensive. RRA and Armalite are good choices; I've used both. The Burris PEPR is an inexpensive and promising newcomer. Look for locking or recoil lugs on the underside of the mount. It helps hold zero when the scope/mount is removed and remounted. Leopold makes a good set of OD rings if a cantilevered mount in not needed.
If you are going to use back up iron sights (BUIS), then you will need a mount that is high enough to clear the folded BUIS. There are charts detailing the various BUIS and mount heights.
Read and research. Many have been down this road and have a parts box full of "attempts to get it right". If I had to do it all over again, I'd go Larue.