Mr556 is a great rifle but there are other guns that do the same thing for much cheeper. If you want to stay piston driven I'd go lwrc otherwise Geissley is probably your top tier duty rifle. If your buying it because it's cool then go for it, nothing says a duty rifle can't also be cool. The stigma about piston being more reliable than di isnt really true nowadays but it does suppress better.

As for attachments I'd recomend something with magnification, lpvo + red dot is the current trend personally I don't get it and would prefer MPVO +red dot or prism + red dot. If you want to stick with the holo sight get a magnifier so you atleast have some capability at distance. Visible laser is really only useful if you also have an IR laser and are using it to zero, if your already dropping this kind of money I'd grab a vis Lazer, IR laser and illuminator unit for night vision capability or just skip it entirely. Also suppressors are cool and you should get one.

If you've shot with a vertical grip before and like it then go for it, otherwise I'd recomend seeing if you can borrow guns with multiple types of grips, there isn't a good or bad grip just get what work for you.

I don't actually own a shotgun so I'll let other people speak on this

CCW - no notes I carry a nearly identical setup, (365x with macro mags) make sure you find a holster that accommodates your light and dot before buying the light, your options are basically streamlight and surefire, good luck finding holster's for other light manufacturer. And DO NOT buy a universal holster, expect to spend 100 dollars at minimum on a quality holster.