The Galaxy Watch Ultra 2 charges fully in about 94 minutes on a 45W wall charger. Jeff Springer ran that test for SammyGuru on a review unit at room temperature with the screen off, using the magnetic puck that ships in the box. He then repeated it on the original Watch Ultra, which carries 590mAh against the Ultra 2's 800mAh, and that one took an hour and 48 minutes. The bigger battery finished 14 minutes sooner.
On Samsung's official 25W adapter the same watch sat at 18% after half an hour and took more than four hours to fill, per PhoneArena. The wall adapter is the only thing that differed between the two runs, though a fault in the single unit tested would explain it just as well. Samsung's product page promises about 40% in 30 minutes without naming the adapter that does it. There is no brick in the box.