What will be regulated will depend on what receiver you have. If you have a pre-ban receiver, you won't- or at least SHOULDN'T- theoretically have any restrictions. If you have a post-ban receiver, you will not be allowed to have a flash hider, collapsible buttstock, bayonet lug, pistol grip or thumbhole stock, or a quick magazine release button (to include bullet buttons).
This is supposing they get everything they want.
Now, this is stupid for several reasons:
-Flash hiders will be banned, but compensators and brakes would not. They do damn near the same thing.
(this is actually why Paul Buffoni had the BCM Gunfighter comp classified as a comp and not a flash hider)
-the number of bayonet deaths in the US is still at zero last I checked
-collapsible AR stocks quickly reduce or increase length of pull. So do most modern bolt action rifle chassis like CADEX Strike-33 (used in the XM2010/MSR and Mk15 rifles) and the AI AX AICS chassis. The chassis are not illegal though.
-Thumbhole stocks would be illegal, but a vertical grip angle on a Manners or McMillan bolt action stock is more of a pistol grip design than a thumbhole. Thumbhole stocks are actually slower too.
Basically, it's all libtard bullshit.