I tend to take a different design direction.
I figure a 20amp 12g circuit is limited to about 75', breaker to last device, by voltage drop considerations. That is not much more than around a good sized room.
I put in lots of 50amp subpanels. Most manufacturers have nice panels that holds 8 half sized breakers. They are small enough to be covered by a picture or mirror. 8 breakers are enough for 600-800 sqft.
My main only feeds the subpanels and 220v loads. No need for it to be large.
