For the amount of traffic that you are anticipating as well as budget considerations, the 711A 433 & 411AR should suit your needs just fine. Of course if you see yourself expanding a lot in the near future then go for more cpu. but based on your information you should be fine.
What happens when one site has a fault? You have too many different types of equipment and configurations. For backup you’ll need nearly a complete duplication of all the gear.
I would change routerboard 3 setup to the same as routerboard 2 but not install the 3rd R52 wireless card (2nd 5GHz radio). Then make up a spare the same as these routerboard 2/3 setups with only one R52 fitted. This will give you a minimum set of spares should the need arise.
I don’t use high power cards at all, because at point to point links i use 0 tx power with big antennas (80-100cm offset dishes with 5GHz feeders) and at APs 10 to 15 tx power depending on antenna.
I mostly use cm9, R52, R52n-M with 433ah and i am very satisfied.