The “look at the block diagram” people are a bit misguided. Yes, different interfaces will always behave a but differently (they often result in different CPU loads for example for a given traffic). But the differences shouldn’t be this dramatic. For example, the L009 has its SFP attached similarly and with no loss of throughput (of course it uses different chips from different manufacturers.) There is something wrong here, but again, given that these are Mikrotik’s first devices on the given platform, and that other manufacturers has similar problems, I’m quite sure this will be resolved with time. By resolved I don’t necessarily mean that everything will become symmetrical across the ports, just that acceptable performance will be possible in every scenario - in many settings the problem doesn’t present itself
In terms of CPU power, the ax2 is to the Refresh, as the Refresh is to r3, so it is a significant increase. It can handle roughly 1 Gbps even without fasttrack. (I’m not suggesting disabling it, just saying…) So in terms of CPU and configuration it certainly can serve as both an AP and the router. (In fact as far as I’ve seen, this is not at an uncommon setup - I used it like this for some time.)
For roaming, capsman is needed. If it runs on one of the APs, the local interfaces of this will have to be configured locally (but this is just setting the local wifi interface to the same configuration as what would be pushed to it were it a slave - so three clicks or so.) Even though in this case the local radio is not “controlled by capsman”, this is the exception to the rule: in terms of roaming it participates fully, the same as if it were in fact managed.
The rest is up to you: is placement/cabling suitable? This only you know.
My personal opinion can be gleamed from the above: I used my network like this without any sort of problem. Some people are of the purist opinion that having one “central” router reserved for only this function is better, but in my view - other than being “pure” - there’s really not much benefit.