I have 26.3 on a test mule and 18.7.3 on my daily driver.
I’m not overjoyed with multiple windows. The split screen in 18 is faster and more intuitive. Whenever I use multiple windows, I spend precious moments trying to get usable sizes.
There seems to be more options in the contextual menus of 26, but maybe I’m discovering options that are there in 18.
Even with reduced transparency, I can’t warm to the visual differences in 26. Some font sizes seem wrong (time, date, connection, battery are bigger than in 18), and when I enable the full LG experience, the fog/mist is inconsistent and distracting.
So after a day of trying to adapt to 26, I return to 18. A week later, I try again. As the OP asserts, the iPad sits in its own place between the iPhone and the Mac, and Apple shouldn’t try to incorporate too many features from the Mac.