I tried ACI through USAA many years ago. There were many restrictions. I finally called USAA back and said they must, surely, offer coverage for a daily driven classic. They then insured the '66 Vette, that was later totaled. They paid up, no problem.
That said...2 years ago I got hail damage on 2 different cars, one with Farmers and the other with USAA. Farmers showed up and paid immediately. USAA wanted me to take the car to a shop with a 6 week backlog for estimates, later sent a drunk to my house who couldn't walk straight at 10AM, cut a check that they stopped payment on, and then low balled the estimate by 1/3 the actual costs. It took 6 months for them to pay up
USAA used to be like family...I have been on and off with them for 34 years. They are now awful to deal with.
Ask me about my slab leak I had with USAA some time...traumatic would be the best term for dealing with them. I can think of no other company that started better and then sank to the bottom faster than USAA. I still have 4 cars with them,because they are cheaper...but I cringe thinking about dealing with them!
By the way, I have never used agreed value or declared value when insuring classics. I take a lot of digital pics and pick up a copy of the CPI for proof of value. I have never had an issue with valuing the cars when a claim was needed.