Wow that thread is amazing. It’s going to take some time to digest and fully understand some of it but an amazing learning thread.Interesting discussion on calcium reactor and pH here:
Thread 'New CaRx - Huge hit time system ph - Help?'
https://www.reef2reef.com/threads/new-carx-huge-hit-time-system-ph-help.933405/
Hope the link works, so the quick notes. Based on my quick reading the idea is to increase the potency of the effluent so you dose less and reduce impact on the pH.
As to your original question, I prefer to run skimmer only (no roller, no socks etc…). In my opinion when you combine systems, none of them end up working well. Also from my experience with socks I found that my NO3 was always elevated 30-50 range, took them out and with skimmer I am in the 1-3 range.
If you want to combine, pick skimmer one size down.
Skimmer should be sized based on the fish load. Corals and especially fast growing healthy corals act as a natural filler. They remove things from water.
Also skimmers add oxygen to the reef tank water, fleece doesn’t.