Whichever one you get both will take 25mm (27mm inflated) GP5000 tires. I have a 2021 Domane SL6. If I was buying today I’d order a Checkpoint with the downtube storage and would stick with a 2x. I test road. SL7 Checkpoint with 1x and did not like the cassette cog jumps on the road. The shop did have the parts for a 2x conversion but that pushed it out of my price range. Maine reason I’d go for the checkpoint is the options for light touring.
Oh I have a second set of wheels planned for the road but switch tires (tubed) now.