A couple of thoughts to consider, @RecoveryRide, after reading the good points already made:
OpenUp, according to its designer, is an off-road setup that does road.
3T Exploro, according to its designer (the same as above), is a road bike that does off-road.
Experiences differ, but my personal take is the OpenUP was a bit sluggish on the road compared to a road bike. Now, I only did a couple of test rides when I was looking for a gravel bike and used one for a Mauna Kea attempt (ie I was on one for many hours on tarmac with 700c wheels). Owning a 3T Exploro since Nov 2018 and putting nearly 4k miles on it just in 2020, it’s a good road bike that didn’t have the sluggish feeling I got from the Open and the Exploro is great on gravel (mountains here in eastern Switzerland, Dolomites, mtb tracks that don’t require serious suspension, etc… a not-aggressive trail ride from yesterday).
A gravel (not CX) geometry, like the Exploro, is likely to be similar to an endurance geometry in the road bike category. If you’re good with that slacker geometry, it’ll very likely work for you. YMMV, of course.
FWIW, as noted above, I’ve been very happy with my Exploro on the road, but if I’m going for a road ride, I’ll take my road bike for a) gearing (my Exploro is 1x) and b) geometry. But then again, due to the trails I ride, I only ride with 47 tubeless tires (usually WTB Ventures), with Byways (smooth center line for more road / speed) and Senderos (chunky for snow, though they didn’t work great this winter) as the alternatives.