Belts and holsters are very personal decisions. I won't comment on the holster since that issue is more complex and requires hands-on time to find what actually fits well for you. However, holsters are another matter and the choices are more limited in terms of form and fit, although there are many choices in materials and style.
For carrying larger guns, what I have found that helps is to have a slightly wider than normal belt, thicker too. I can get away with a 1" belt for normal pants and no gun, but 1 1/4 or 1 1/2" is more comfortable for a bigger gun, say a full size 1911. I find the wider belt holds everything more securely as it has a wider surface area to do this. Most jeans seem to do okay with up to a 1 1/2" belt. Dress pants may be a little trickier to find loops that big, but the Dockers I have do okay with them. By the way, I wear a 34" waist. Belt loops seem smaller for pants 30" and smaller, to cross check the belt to the pants.
The belt ends up riding on the hip bone, sooner or later. As such the wider aspect and thicker too will help to keep there from being much discomfort as compared to a narrower and thinner belt that may tend to dig into you.
All leather belts will stretch and conform to you. So don't let your first wearing or two get you down if you find you have a sore hip or other part. This passes quickly as the belt does its thing and becomes personal to your form.