Welcome! You should start this post in "General Modeling Discussion" and you'll get a lot more looks. Or "Ships", where you'll get fewer but interest from people who can answer.
Putting aside brand question for a bit.
For scale, there are a number of factors; storage space and time of build being two prominent ones. Expense a close third, followed by availability. And you mentioned a diorama. If it's one, it's huge in any scale.
Time of build and availability are the only two choices that aren't personal for you. A 1/350 scale model is eight times larger than a 1/700 scale model. A 1/700 scale aircraft carrier might run around $ 30 - $ 40 to buy and 3-4 months to build. A 1/350 scale aircraft carrier might run around $ 80- $100 to buy and 6-12 months to build.
As far as availability, when you say "each class", I assume you mean general types. Otherwise, just the USN alone had three classes of fleet carriers, three one offs, and probably five or more escort classes and a light carrier class or two. Destroyers, I have no idea but probably at least eight.
In terms of the more general types, in 1/ 350 you'll have no trouble finding each of the four types you list in plastic for the IJN and USN. You'll have no problem with the DKM except for the lone aircraft carrier, which isn't around in 1/350 AFAIK.
The RN is harder. As the UK is a metric country, their scales are decimal for aircraft carriers.
All of these factors become simpler in 1/700, in particular if resin kits are considered. They are just, well, smaller.