Ever cleaned a fx6? Complete pain. When from fx5 on my tank back to 3 ac110s on my 180. Eheim is better biological and design seems easier to clean but no experience with it.
The need for 1 or 2 filters is based on your bioload. If you’re overstocked you’ll need 2, if you have minimal stock you can probably get away with one and then some powerheads for extra movement.
I dont think the fx6 is that bad to clean. You can just take the whole stack of media out and dunk it in tank water. Takes me like 5 minutes.
I do like the idea of 3 ac110s. Thats actually how i would run a 125 with no plumbing. 3 big hobs right across the back. And it would be comparably easier to maintain.