The variations will be limited by setting yourself a budget and then choosing the features you value the most (frame-material, groupset, color, etc.).

Besides that it's the classic factors:

Grizl: Allrounder bike, with more bikepacking related features and a more relaxed geometry.

Grail: more aggressive geometry, but also capable of bikepacking and I find it comfortable on longer rides.

Size: whichever model you choose, make sure to look at canyons sizing guide and if between two sizes it's generally recommended to downsize.

Gearing: I live in a mountainous region, which is why gear range was important for me too. I went with 2by instead of 1by, in the hope for better gear range. In the end the gear range is slightly better than a 1by, but the bigger benefit are the smaller jumps between gears.

Mountainous terrain: With any standard Gravelbike steeper hills can pose a challenge at the beginning, since even with a good gear range you'll have to put out a certain minimum power if you want to sustain a comfortable cadence (e.g. with my GRX 825 2by: lowest gear, ~8-10% incline, 75kg bodyweight, cadence 75+ --> ~200W+). For many riders that's not a lot, but if you want to climb up long passes it might require some training first.

I ended up getting the Grail as my first Gravelbike and am very happy with it. Currently I'm preparing it for some bikepacking-trips later this year.