I’ve got the Ergodox, so my recommendation is entirely off the strength of that product. If I were buying from them today, I’d probably get the Moonlander, but that’s because I use my keyboard with my home desktop 99%+ of the time. If you plan to travel, commute, or otherwise use your keyboard in multiple places, I think the low profile keys will be perfect for that.

As for add-ons, there isn’t really anything to add for the Voyager. If you’re considering the Moonlander, I would be tempted by The Platform. It’s a full third of the already hefty price of the keyboard, but it looks like the dream tilt solution. The legs on the Ergodox, which look to be the same legs as on the Voyager, are serviceable, but the interface that keeps them in place can wear out needing replacement, and they can only tilt so much (the Voyager has less I believe, so you can still tilt it but at less esoteric angles). The platform will let you get nearly vertical with each hand if you want, which is kind of the ergonomic dream. Although, tbf, after using my Ergodox for a couple years, I rarely tilt it at all and just use it flat on the desk along with the included wrist/palm supports