https://www.gggaz.com/benelli-m4-tactical-charging-handle.html
https://freedomfightertactical.com/collections/most-popular-benelli-m4-upgrades/products/the-freedom-fighter-tactical-half-inch-diameter-steel-tactical-charging-handle-for-benelli-m4-shotgun
https://www.gggaz.com/benelli-m4-tactical-bolt-release-pad.html
https://freedomfightertactical.com/collections/most-popular-benelli-m4-upgrades/products/the-fft-oversized-bolt-release-button
My M4 came with ghost ring sights, so not sure what you mean by these, but I did change out the front sight with Blitzkrieg Componets front sight.
https://www.blitzkriegcomponents.com/benelli-beretta-chevron-front-sight--short--lumi-green-tritium-dot.html
I don't have an optic on mine and I am still going back and forth if I am going to get one, but if I did I would go to scalar works website and get one of their setups or just put an EO Tech like you mentioned because those things are just tanks and I love my EO Tech on my rifle.
https://scalarworks.com/shop/integral-mounts/sync-01/
I have a Carrier Comp full-length mag tube and I could'nt recommend them enough. Their customer service is A+++ and the product is a 10/10. I personally do not like the 2 round extension but that's just my thoughts others may like them.
Oh the infamous Black River products. Yeah, I have tried emailing them multiple times and have never received a response from them and I have yet to find a review of anyone putting one on their legit Benelli M4. They are a Turkish manufacturing company so to say and they put them on their faknellis so I would not spend the money personally on it, but if you do and it works out please let us know.
I see a lot of people who like the midwest handguards and I have heard of some that dont. I have the 13" Briley hand guard and absolutley love it and would fully recommend it to anyone wanting a new handguard on their M4.
https://www.briley.com/p-63643-briley-3gun-m-lok-handguard-benelli-m4.aspx
Hope this info helps out and points you in the right direction. Things to put on your shotgun are very subjective to the individual and some may like certain items and some will not so it will be up to you to do as much research as you can to find what you need and want. Let us know what you end up going with and please share some pics I would love to see them.