Right down my alley.
My dogs, German Shepherds, average 90-120 lbs and are working dogs all. From tracking to protection.
I have a couple of 2" wide "agitation" collars that I use for bite training. I used 6 oz doubled. This is not an everyday collar. The width is more for the dog's throat protection and comfort than for security.
Normal day to day collars are 3/4" or 1" wide, 6 oz doubled. I've also got a couple of 1-1/2" wide collars.
I sometimes think that doubling is overkill. Latigo is good, but keep in mind that latigo is what the tannery designates as latigo. Your hardware choice is just as critical as the leather itself. O-rings and D-rings need to be heavy duty and welded.
For leads, I just use an 8 oz strip (single), 3/4" or 1" Wide. I add a piece of "wear leather" around the loop where the spring clip is attached. I use a square eye clip vs a round eye.
I don't build my collars or leads to impress bystanders. If I want to do that I slap a muzzle on the dog. The collars and leads need to be light, but strong enough to do the job. If you're worried about a dog breaking a collar or lead, the dog needs more training not to be pulling. Tracking dogs will not pull so much as they forge forward. It's the handler's job to keep up. If you're sending a dog out on a bite, once the dog is fired up and starting to lunge, it's time to let the dog go.
Have fun and g'luck.