Lots of suggestions here! I'm trying to think of a midsize dog that is short haired and usually well endowed.
I had a 90 lb boxer. He had 7" and was very friendly. Their young years through mid life they sure like to run hard and lung forward running like a racing breed.
The weimaraner is high energy I guess. A German couple had posted multiple vids of her mating with theirs. They went by weimaranerrude. I think his cock was a little on the thin side, barely.
Beagles are a small dog with a nice size, and sometimes maybe better height / reach than others when on all fours / doggy position.
German shorthaired pointer. Maybe they need more space, but they're both a good height and usually have a wide knot. This makes me think of cur dogs too, or those mixed hunting breeds that have short hair. Their usually less chubby than a lab, about the same height, and hung.
Brazilian Dogo might be at the large end, and I guess larger than a lab.
Bull mastiffs are shorter, but heavily built. In the vids of Barney & Frankie, they had a 6 minute tie once, and other vids of bull mastiffs show a large knot. I think they will slobber a lot. The boxer slobbered a bit.
I guess the mid size hunting dogs that aren't the most hyper, will probably be about right. The American Bulldog is kind of like a large pitbull, and the ones I've been around were friendly. The one Brazilian Dogo I was around was a lot like an American Bulldog, but taller and sweet. The guy I knew had her to hunt, but she didn't want to hunt. She went to someone else to just be a pet (lucky her).
I'd try a cur dog myself, as a next breed for me (mostly for women), but my living situation would be different. Otherwise, probably the largest beagle I could find, or similar hound that wasn't too low to the ground.