I use equidistant spacing a lot and i’ve seen good harvests, but i also find it difficult for succession planting… garlic -> kale for example.
off: Sometimes it’s ease of harvesting, weeding… row spacing is quite amazing, especially when the soil inbetween is mulched and planted with early crops. For now i only sowed fava beans and parsinps in a garden and i used rows 30cm apart as i will try with early crop of salads, spinach and radishes inbetween. Later on late brocoli, cabbage etc will be planted inbetween maturing fava beans… parsnips are much easier to weed/mulch in rows.
Anyway, i’m a big fan of equidistant. Planted beetroots were amazing last year, also peppers, salads, chicory, celeriac, garlic and many others.
To go from rows/plants to equidistant, i just keep the ratio, i give from row to plant and i come to eq. For example 30cm for rows and 10cm for plants = equidistant is 20x20cm.