Just a note, I have decently low ambient CO2 and a CaRx. I don't measure pH regularly but I can say that I run about 8.2 on the peak. IME the ambient plays a much more important role than practically anything else.I will defer to the calrx experts out there, but I do know they depress ph.
I have moved from my house that I installed an ERV and I am now in an apartment. Fortunately the air handler in the apartment has a fresh air pull. I can still get the occasional 1000ppm period but it doesn't happen often and I often correct it by running the AC more (ouch) or opening the windows a bit to get in air. My normal CO2 is usually 450 - 600ppm.
I just can't see how fighting the ambient with either a scrubber or an outside airline makes sense. This is an expensive and often useless way to deal with an issue that not only effects our tanks but also our health. IMO better to deal with the root of the problem than to continue to band aid the symptom.