"jeff" wrote:

In general, would you say that if the goal is to heat everything but the
basement, then there is no reason to have vents opened in the basement
itself as long as there are enough return/supply vents on the main floors?

Personally, I'd like to make the basement part of the air space. I have
an open (no door) stairway, so it isn't sealed off any way.

Making it part of the air space would go a long way towards
de-humidifying the basement, something that many need.