Re: No trunk lines off of furnace?
They usually call those "octopuses". IN some cases, these were originally gravity furnaces, that used convection with no blower. Sometimes the ducts were asbestos insulated.
If it's a older furnace, it may have fairly low airflow if <80% efficient) and just isn't moving a lot of air. IT might also be oversized and has too much restriction so much of the heat goes to air leaks.
Hard to tell form here.
IF there are no trunks, then the supplies might be locted in the center of the house and just aren't distributing the air well, and it instead short circuits to nearby returns.
Finally if you have too many registers, you "throw" or velocity can be too low to mix the air.
I think you need a pro to come look at it and recommend a solution when they replace the furnace and ac.
1925 Two-Story Stucco Beaux Arts Neoclassical