I would say it depends on what you want to do? You can edit plenty of things without ever using the render window. Why not give it a try and see for yourself?
This.
And you might have to close the render window to avoid it svcking processor cycles anyway, but everything else other than on-the-fly rendering (which is indeed slightly less demanding than actually playing, because a little stutter isn't an absolute killer) is processor-intensive but not time-sensitive.
In other words even on my quad-core 3.2 GHz processor it takes a minute to load the BSM, but that doesn't really matter because lag doesn't make the program unusable.