Exo Mountain Gear also has a modular system. You can get the frame sized for you, belt sized for you, and different bags that will/can work for your purposes. Like others have said, the frame needs to fit you comfortably and the bags can be configured to your needs.
I have an Exo K2 3500. I added the meat shelf bag, multiple organizer pockets, weapon carrier accessory and two belt pockets. I can run my holster on the belt, I have also bought the K3 1800 bag which works great on the K2 frame. I also purchased a small belt to swap out to when I had lost a bunch of weight and found the medium fitting me too loose with weight.
My 3500 bag compresses down to a small size. If I am truly hunting from the truck/ATV or from a base camp, I find that the 1800 pack is perfect, but I run the lid with it as well.
I have an Osprey Atmos AG backpack for backpacking. I used it a total of ONE time. It was comfortable, fit well, was a good backpacking weight and I enjoyed it except for the squeak it developed on that first multiple day backpacking trip in the High Uinta Wilderness area. For hunting, I used to run a Badlands 2200 internal frame hunting pack. I thought it was good and hauled many quarters on that pack and was so grateful for the meat shelf.
When I moved to the "then new" EXO 3500 (generation 1 version) and got to haul an animal in it, I was blown away. The pack was roughly the same weight, but it could be bigger significantly, and it was so comfortable to wear all the time while hunting. But the first time I put animal weight on that pack (see my profile picture), I really understood how big of a difference a pack meant to haul meat (weight, shape, etc.) was. It was a game changer. Such a huge difference. But I likely wouldn't have arrived at that position had I not worn the pack while hunting. It had to be comfortable. The EXO excelled in this regard. And the K2 version was more better. I sold the Badlands to a buddy that wanted it (still feel bad about this.) and I have never used my Osprey again as I prefer the EXO in every way. Guess I should sell that Osprey, but had held onto it for my sons or wife to use if I could ever talk them into backpacking with me ever. Haven't been successful in that yet.
MR, Kifaru, SG and EXO would all be worth consideration. I am personally a fan of EXO due to the fact that their products work, are great quality, are comfortable, and also very important---backed by an amazing customer service experience. Customer Service can't be any better than what I have experienced with them. No need for me to look elsewhere at this point.
FH