Before you even buy anything, if it’s work related and you’re in pain (I was when I started down the rabbit hole), drop some coin on the Kinesis Advantage 2. That will get you some experience with a keywell keyboard, a mild split, some ortholinear/columnar and mechanical keys. That will help determine if you can live with all those changes all at once. Whether it works out or not, you can easily return it on Amazon.
From an entry level perspective, I recommend a Moonlander. Programming is really easy and has a GUI that makes things easy peasy. I created a custom layer for my type of work in the first 30 minutes of opening the box. You can get the Platform, which is a separate tent rig for the Moonlander and adjust the thumb cluster to fit your hand size. And the keys are hot swappable - which you will want when you realize you can control the different sounds and actuations of your keys. As far as the number of keys, one word - layers. The less you have to move your fingers, the happier your hands.
From a support perspective, Robin at ZSA was amazing! I had an issue with my right keyboard and it was handled in a timely manner. The only thing they didn’t do was swap out my keys for me.
Good luck!
Have you checked out Razer Pro Type Ultra?