Shape and letter arrangement are separate choices
A row-staggered board offsets each typing row. An ortholinear board aligns the key columns; a column-staggered board offsets columns instead. Split describes separate hand sections and can be combined with these geometries.
Compare the positions your fingers must reach, especially the thumb keys and outer modifiers. The illustrated split and ortholinear boards show a 48-key planning pattern; actual boards can retain different keys.
Plan the missing actions
Small boards often move digits, function keys and navigation onto layers. Choose a reachable layer key, put related actions together and keep frequent modifiers usable at the same time.
Colemak-DH has separate row-staggered and ortholinear arrangements. Choose its matching variant when planning the key positions.