Thanks all, again.
So it seems like there are 2 clear ways of thought among you guys -
some say - just go with low poly + normal maps baked on them from high poly,
while some same - start with low-poly, and then one-by-one start replacing them with high-poly (how would that workflow work ? i.e. - I start replacing object, and half way through I notice a performance dip - now I have a room with 50% low-poly objects and 50% high-poly objects ?)
What about my comment on levels ? Does splitting each room in the house to it’s own level (hope I’m using the term levels correctly) help with performance / memory at all ? will this approach allow me to insert more high-poly models per room ?