This is where I began. Looking at a recommended ID rim width versus tire width chart.
https://www.wtb.com/pages/tire-rim-fit-chartDepending on the generation of gravel bike frame you have, you may only be able to install up to 40mm wide tires. New generation gravel bike frames can be purchased that will fit up to 2" tires / 50mm tires. (
Remember that the wider the rim, the less side wall bulge you might have. This can lead to rim damage if you run too narrow a tire on a wider rim.)
I started out thinking I could use my gravel bike for gravel road bicycle touring and discovered that my gravel bike was limited in how I could configure it and that it beat the heck out of my upper body descending. If you want to participate in "bikepacking rides / events" where you carry a minimum amount of gear and are riding for fast "best known times" then you will want to ride on as narrow tires as you think you can get away with. You will want 700c rims with an ID between 22 and 24mm.
It you want to bike pack on rough terrain where there is a lot of chunky, washouts, washboard, and overall crappy riding conditions, then you might think about a 29er hardtail with rigid fork that will fit 2 to 2.2 low rolling resistance tires.
I built up a 29er hardtail that I run either a rigid carbon fork or a suspension fork, and use drop bars on this bike. It served me well for over 1000 miles of camping this summer.
Take a look at what the 2023 Continental Divide riders were riding to get a feel for what will meet your needs.
https://bikepacking.com/bikes/2023-rigs-of-the-tour-divide-breakdown/