I'm waiting on my rifle can but have rimfire and pistol cans. Subsonic is the only way to get really quiet. 5.56 can be difficult to tame with longer barrels, shorter ones are even more harsh. 300 Blk is the best of both worlds as it is super and subsonic capable.
I made my own trust with some Internet research and Quicken. It worked just fine.
Surefire cans perform well from the reviews but are way more expensive. The value just doesn't seem to be there as suppressors at half the price will perform with 95+% or more comparatively.
There are many forums and online resources to answer many of your questions. Cans are expensive and come with a wait only our federal government can create so save your pennies and do it right the first time.