Are you not worried about the size of the Pro Max? I am also with iPhone X but I think the Pro Max is too big. I was thinking to order it because of the camera improvements but I think I could regret the size and not be easy to use it with one hand...
I had a 7 Plus before the X, and the 12 Pro Max has the exact same width as the 7 Plus, so it should feel similar in the hand (maybe even better because I think the flat sides will be easier to grip). I do like being able to do everything on my X with one hand, but then again, I've also been annoyed at how small the X screen looks when watching YouTube videos in bed, which I do a lot of. I also work from home 100% of the time now, which makes owning a big phone less of a hassle. And one more thing... I miss the insane battery life of my 7 Plus. When I owned a 7 Plus, I would end the day with like 40% remaining, but even when my X was brand new, I would often end with only around 10%, so it didn't take long before the battery degraded a bit and I had to start charging at some point every evening.
Bonus tip: I found that having an extremely grippy case really helps you to be able to use a large phone like the 7 Plus with one hand, because you don't have to put your pinky under the bottom or wrap your fingers all the way around the far side to hold the phone, which leaves your thumb with a lot more mobility and travel distance. The Apple silicone cases are perfect for this, and I may try a Caudabe Sheath with my 12 Pro Max as well. I used an Apple leather case with my iPhone X, but I don't think that's going to work with a 12 Pro Max because it's too slippery for that holding style.