I started with space on the right mainly because I used to type like that on a 60% keyboard. Then swapped to make gaming easier and I really wanted to keep a single layout so that I can easily chat during gaming without switching layers.
Next, I wanted to learn a 3x5 layout for possibly building such a board in future and took some inspiration from more compact layouts. Now I have shift on the right and enter on a layer. Here's my layout I've been using for months now: https://keymapdb.com/keymaps/ranzq/