I don't want to complicate your decision making process, but other things to consider if you want your bike to double as a Bikepacker.
- Bottom bracket choices: I am an advocate for the frame having the most common bottom bracket. I prefer only BSA or DUB. Reasons being. If you get the bug and start riding existing 500+ mile rides, you will find that the route organizers just love to put in a lot of creek and river crossings. This means that your bottom bracket will get soaked numerous times. If your bottom bracket locks up, gets loose or squeaks, you will be glad you chose the most common BB standard that a remote bike shop might carry.
- Rear hub width/standard: Most modern gravel bikes use 142 rear hubs. From my perspective, I want to stay with the boost standard for most of my 29er bikes. I have built up several spare wheel sets. Therefore, I want my bikepackers to have 148 hubs. (Hence, my draw towards using a hardtail rather than a Gravel frame for my bikepacking rig.)
- Tire Size: I want the option of being able to run up to 2.2 tires. The larger tires let you have a more comfy ride when packed up and you don't need a front suspension fork.
- Carrying cargo: I have a 29er carbon fork that has eyelets on it so that I can mount things on front without using clamps. My 29er has a shorter head tube, so more of it sticks out the top. I have been installing a second stem below the handlebar stem that is used to mount my front handlebar cross-pack on. On the back, I use a dropper post, and I use a bike rack seatpost clamp that lets me mount a rack to the back. Instead of depending on mounting provisions for a rack on the frame, I use a "Robert Axle Project" thru axle that has mounts on the side that hold my rack. I like the wider 148mm frame that helps triangulate the rack side-supports and creates a stronger rack overall. A lot more side-to-side stiffness than I had on my gravel bike rack.
- 1 X 12 or 2 X 11 or12: I have gone down the path of using a 1X 12 set-up. Not having the front derailleur is one less thing to fail on long trips. Having 2X front is nice when you are gravel grinding or road riding, where you want/need to ride faster. When you are loaded down with gear, having a 2X set-up doesn't gain you much average speed wise. Many gravel bikes are still set up for 142mm hubs and a front derailleur. Another reason I went with a 29er frame. They are designed for 1X set-ups.