We always use the blue filters, first thing on the campground spigot.
I've never used a "good regulator", we use a shurflo extreme 65 psi pump, few campground are anywhere near that.
Charcoal filters, and that includes the blue one, remove any chlorine in the water. So if that is attached when you fill your onboard tank, the water is more likely to "go bad"
You do want to sanitize the entire system with a bleach solution annually or more.
We have a sani-con macerator, and I have to pay a bunch of attention to dumping and pumping.
Most of the others at our seasonal campground, TT's and park models, must just keep their valves open, cause I never see them dumping or tending to the situation.