I'm running 3/4" from compressor all the way to the filter dryer, the inlet of the filter dryer is 1/2" NPT, the outlet of the filter dryer is 1/4" NPSM, will this setup be good for painting?

Out of the regulator(on the dryer), I have 25' of 3/8 hose, but I don't think it's long enough, will 50' be too long, too much pressure drop?

My setup is completely different than yours (a/c condenser, fan, water trap tank), so I can't comment on the piping.

Make sure you replace those industrial type connectors with high-flow connectors, like Milton V-style, if you haven't already. Makes a huge difference in air flow.

Twenty five feet is too short for my shop by about two feet, so I'm picking up a 50' hose this morning before I BC/CC. I'm going to cut it down some so I'm not stumbling over all that hose.

Here is a calculator for pressure drop. http://www.engineeringtoolbox.com/pressure-drop-compressed-air-pipes-d_852.html

The air leaving my main tanks is very dry, so I added a quick disconnect before the QC-3 so that I can run my air tools without using up m desiccant.

One thing about the QC-3. The indicator on mine started to change color very quickly, like the next day, with minimal usage, never a droplet of water in either the pre-filter/separator or the QC-3's trap, and barely a 1/2 teaspoon of water draining out of the main tanks each morning. I'll just replace the desiccant cartridge before each project and ignore the indicator.

Thanks, I was thinking about having a Tee before the dryer so I can by pass it.