I've carried concealed in shoulder holsters, and mostly horizontal shoulder holsters, for 30 years. When I lived in a cooler climate I carried this way every day, now I usually only carry in a shoulder holster in the winter or when riding a motorcycle. I like carrying this way, it's far more comfortable to me, I hate having a lot of weight on my belt, even with a stiff gunbelt. Even when belt carrying, which I do most of the time now, I use a stiff gun belt and the super duty Perry suspenders, which transfers most of the weight to my shoulders, letting me keep the belt one notch looser.
Lots of good holsters on the market, just be sure to get one with wide straps and a double or triple mag carrier on the offside to balance the rig. Without the balance weight you'll either end up with an overly tight elastic strap on the offside, or having the offside connected to the belt, something which I find to be uncomfortable. I much prefer the rig to be balanced, adjusted to ride high, and having no connection with the belt on either side.
Of course, what you find most comfortable may vary.