It really depends on what you're most comfortable with; when you go for such a custom option most of the design decisions are about personal preferences.

I suggest you draw out some layouts on a piece of paper, adjust them until you feel happy and then plan out how you want the keymap to look. When you're happy, look for a layout that fits what you want or build your own on KiCAD.

I bought a kyria from Splitkb, and I've been very happy with the design. If I needed another keyboard, it would probably be a very similar layout, but have slightly fewer keys, be low-profile and no oleds.

Split keyboards are niche enough that the cheapest option I found was building it myself (with pcbs by jclpcb). Ones I looked at are corne, cheapino, lily58, and ferris sweep but I settled on the chocofi and have been loving it

Edit: my goal was to find something "corne-like" as there seems to be good resources for it and I wanted to try the miryoku firmware

I liked the SplitKB Kyria. But my wrists did not (through no fault of the keyboard - wrist injury).