I work outside training horses and farming so I am out in the weather pretty much all the time. I very rarely switch guns or holsters, sticking with a 4" M&P9 compact on my belt.
A big consideration in coats for me is to find them with a 2 way zipper on the front. A coat that is long enough to cover the gun, but can have the bottom of the zipper undone to waist level is nice. If it doesn't have that, it has to fit pretty loose.
I also wear carhart bibs almost every day once the temp is staying consistently below 40 and that can be kind of a bear it your holster doesn't line up with the side of them. I have that worked out pretty well and don't try to change styles of bib, or holster for that reason. I usually don't need much more than a medium weight coat over the bibs if I am working, so I just tuck my shirt behind the gun when the coat is on so that I'm only clearing one layer.
If it is really cold and I know I'll be standing around or sitting on a tractor or something most of the day then I will add a pocket gun like an LCP to my coat, or in my bibs.