Hi there

Regarding the interior I would use Area lights,sometimes I use more than one,usually I end up with 2-3 and one Infinite light with enabled shadows,regarding the point lights,are you have enabled on them Inverse Linear or Lineal Square ?

Here are two quick renders

In this one I've used 2 area lights and one Infinite light with intensity 100% with enabled shadows plus BB EnvSphere,still is grainy(only 25 samples)

And this one,there I've used 3 area lights with one infinite light and BB EnvSphere

Regarding the lights again,you need to find yours way how to light the scene,usually for portrait renders I use 3 point which consist from Area light with spotlight and one infinite light

Hope this helps

Thanks,Jura