It depends on the situation. There are certain parts that won’t work as well with a modular workflow–like walls/ceiling/floor. Luckily those are very simple so if you can keep a flat surface as a single mesh without splitting it up then you will get good results. Walls can be split at the corners, floors can be split if there is a flooring change. Most of the time what people try to use it for is stuff that doesn’t benefit from modular construction anyway–floors and ceilings are usually very very simple. The only issue there is that you might not get enough detail in your lightmap even at the highest resolution which would require you to split it up.