If you can, go ride a Surly Cross Check and a Surly Long Haul Trucker. Both are super versatile and perfect for what you are describing.
To determine size, the bike hermit has a blog post on measuring your PBH that is super helpful. I smile because a fellow stopped in the other day and said he spent $400 with a bike fitter so out of curiosity the bike hermit measured his PBH and the saddle set up was less than 1/2cm different.