I updated my first post with an update on my progress and thoughts about the layout:
Update (2022-02-22): It took me approximately 2 to 2.5 months to gain speed in Colemak more or less equal to my best QWERTY speeds.
I have stuck with my initial plan to use Colemak-DH exclusively on the Moonlander and use QWERTY exclusively on all row staggered keyboards. I have been surprised by how little I've used a row stagger keyboard. Basically, I have only been forced to use QWERTY when interacting with other people's computers (which is fairly frequent but always extremely brief). As a result, my ability to do my normal work on QWERTY is probably extremely hampered at this point, but I'm not worried about it. The Moonlander has proven portable enough that I just take it home with me on the weekends and to off-site locations if I plan to spend anytime working on my laptop.
I have been very happy with Colemak-DH and made only one set of changes that are fairly small in practice (replacing Z with ' and ; with -). The motivator for those changes was to move the ' off of the right pinky, because I really dislike how it interacts with the other punctuation (particularly the comma and both slashes) when it's on the right pinky. As an added bonus, having the ' on the bottom row of the left pinky has transformed all of the common contractions and the possessive 's into really comfortable rolls or hand alternations.
If I could go back in time and remake the decision to learn an alt-layout, I would do so without hesitation. I would probably stick with Colemak-DH (with my minor alteration), but I know longer really care about maintaining the ctrl-Z, X, C, and V shortcuts nearly as much, so I would be tempted to try something more exotic like Semimak or Engram. But, I can't see any super compelling reason to choose against Colemak-DH, unless you hate alt-fingering NK / KN.