I think my folks did 30x36 as a great room, kitchen/living room with 2 couches, 2 reclines, bay window seat , sideboard, island, counters on 3 walls, 2 ovens, 3 sinks, 2 dishwashers.  Plus a bump out into garage for bathroom.  You can seat at least 20 people at one table for family dinner and there is another dining room that seats 10, family room that can seat 10 before getting out folding chairs, and then we get out round tables in the HVAC’d garage.  Center of the family activities.