A suppressor is nice, but also adds length. Think about your use case and whether that makes sense. Also, in the US you have to get on a government registry if you get one. May not be much of a concern since you’re already on a registry if you buy a gun. (I know they say there’s no registry, but do we really believe that?)

When training I recommend doubling up on hearing protection. Have some ear plugs and then electronic hearing protection over top. Walkers are cheap and work well enough for most people.

I would actually suggest getting a rifle in 5.56. The pressures are a bit higher than .223. You can shoot .223 out of a rifle rated for 5.56, but not the other way around.