I own an SBR'ed 107-CR. I cut/crowned my own. Its really a pretty simple task requiring only simple tools and a relatively inexpensive crowning kit. No need to pay a smith as it is a simple job. As for engraving, I used a company here in the Kansas City area called Acculazer. They did a very professional job for only $20.00 while I waited. These guys engrave a lot of NFA stuff and come highly recommended.
If you're looking to stack ammo deep for storage, I'd try to track down whatever you can find that is factory sealed in spam cans. For general plinking, just about any ammo will do. For your go-to, home defense,shtf mags... I'd load with either one of the premium loads from Hornady, something older which uses the 124 grain 8m3 Sapsan bullet, or something along those lines.
Finally, you asked about drums. Personally, I've never cared for them aside from novelty purposes. The last time I owned any was during the assault weapons ban. The only ones I owned were the Chinese variety as the were loaded from the back and could be stored without tension on their springs even loaded as they utilized a cranking key on the front to establish spring tension. They were heavy when loaded, awkward to manipulate, threw off the overall balance of the gun, and created a rattle when moving that used to drive me nuts.
Hope I covered everything. Welcome back!