Somewhat tangential to your question but before you go custom, join this FB group if you’re not already in it (Dressage Boots Addicts Anonymous):
https://www.facebook.com/groups/580640726303352
Even though it says dressage, you can pick up some great deals for all kinds of boots. And there is a ton of personal experience and anecdotes there for good and bad companies to order from.
I’ve picked up a few custom (used) boots there now. What helped was knowing what boot brands fit me, not my actual measurements. I know that sounds backwards, but it’s like a horse’s back and a saddle - just because it’s stamped MW doesn’t mean it fits. On paper, my measurements are 39/43/38 - which is apparently a nonstandard size… but in practice, I can fit into Deniros MCL+ sizes, just about any tall Kingsley, and a ton of different Celeris ranges.
Back to your question on who makes your favorite customs, reviews seem all over the board with brands and favorites. Since you’re a non-standard size you should be able to find something there, as that group is naturally going to attract people with nonstandard sizes.
I love my Celeris Bias, btw. Bought them for half of what they go for custom new, and never get tired of looking at them. I see a lot of people happy with Deniro and Kingsley, but then I also see posts regularly that say “selling because they don’t fit me”… so… it’s a toss up.
As with all things in life measure twice! 