Typical disclaimer: state laws may vary and this is only my experience
I can't help you much as far as being certain all the extras are covered but my brother had a similar incident that I will describe to help you understand how the buy-back process goes...
My brother had a newer, somewhat expensive truck $20-30k that he had added ~$8k in add-ons (different wheels, AL flat-bed, fuel tank, tool-boxes, custom bumper etc.
He totaled it by driving through a garage. Frame/suspension was junk (concrete stub-wall), most of the front body work was damaged, but the back half was good (where most of his add-ons were). Insurance totaled it, payout was a bit over blue-book value which came up just a little bit shy of paying for what he had in the truck.
Considering all the add-ons were good and the engine (Cummins diesel) and transmission were good, and the truck had the premium interior, he decided to buy it back. He had to pay 18% of vehicle value which is fixed at that percent no matter what (that's either state law or the ins. co. policy, I can't recall which but I want to say it is state-law). So for 18% of the value he bought the truck back, took his $8k in upgrades off, removed several of the nice features of the premium interior so that he could install them in his replacement truck, sold the axles to a guy that was going to repair them, and sold the truck carcass with engine/transmission. All-in-all, after he was done removing upgrades he sold what was left of the truck for MORE than it cost him to buy it back. IE, with the insurance check (minus 18%), keeping his upgrades, and selling what was left, he GOT PAID to have an accident...
YMMV but I'm going to assume that this isn't the only occurrence of insurance buy-back value being "fixed" no matter what the real value or actual damages are...