So far, although still only in the first week of using it, I've found the "VFR" maps pretty useless, particularly in the Bush activities. Real VFR maps are highly detailed showing highways, rail lines, power lines, larger vertical structures, and details regarding every public and some privately operated airports including elevation, runway length, availability of lighting etc. They are very useful for the basic flying skill of pilotage which is essentially what the Bush mode is supposed to represent, i.e. flying with respect to known physical characteristics of the land around you. About the only way the MSFS 2020 "VFR" maps are useful is that they show water ways and ground contour and the location and runway orientation of airports similar to but way less detailed than real VFR Sectional or terminal area or the broader area VFR flight planning maps. And with a lot of pilots these days using cellphones and tablets to track their flights in real time with the detailed sectional and terminal maps, it's comical to me that they put up these nearly useless VFR maps that don't support even simple pilotage by providing references like roads, rail lines, city boundaries, and power lines. No one in this day and age would fly into unknown territory without as much detail as they could find to carry with them.
As to the isogonic lines option, isogonic lines describe the perimeter of areas of equal altitude and augment the basic coloring running from MSL in light blue through green, yellow, brown, etc. representing broad scale elevation changes. And that's about the only part of "VFR" maps they got right.