Yes it will increase the build time but compared to the other settings, it’s really not that bad. I left indirect lighting quality to 1, bounces to 10, smoothness to 1 and it’s the defaut baselightmass.ini. I really only used a scale of .4, uncompressed lightmaps. 
My previous version took 16 hours and looked worse with the other settings cranked up. This scene lighting is simple tho, just a skylight with Epic’s HRDI.
Also, by leaving the rest of the settings to default, I was able to raise the resolution of my lightmaps to 1024 to clear all artifacts, something impossible in my previous attempt that took 16 hours with 256x256 lightmaps :-S