For my indoor level I used 1m = 128 quants. It allows me sufficient details.
For the rooms this gives me realistic values with:

Roomhight old house 3m = 384Quants = 3x8small boxes = 3 big boxes

Thickness betwwen ceiling of one room and floor of room above = 0.5m = 64quants = 1/2big box
half of it gives me thickness of ceiling and thickness of floor for each room: 32 quants = 2 small boxes

Wall thickness outer wall =37.5cm = 48 quants = 3 small boxes,
Wall thickness inside, load carrying = 25cm = 32 quants = 2 small boxes, gives me 1 small box per room

stairs: 1 step = 25cm high = 32quants high = 2 small boxes high
1 step = 31,25cm deep =2,5small boxes deep

And then I did the same like HeelX: create a reference cube 1x1x1m = 128x128x128quants and export it to my other modelling tools as "urmeter"