I DM a campain with an arc set in a ruined fortress in which the PCs first fought and defeated the invading orc horde and then discovered and explored the dungeon below.
We use Roll20 both in person and remotely as an electronic grid. In person we've played where everyone brought a computer and also where we just had one map displayed on a big screen.
Often we just sketch out a scene on the Roll20 grid, but I have drawn numerous outdoor and indoor maps.
The dynamic lighting and fog of war features in Roll20 allow me to expose only part of the map at a time.
For the arc taking place in the ruined fortress I drew floor plans and elevation drawings in Inkscape, then imported them into Roll20. The setting is quite 3D, with multiple buildings and towers in the fort with multiple levels and with multiple levels to the dungeon underneath.
We use the floor plans as Roll20 maps with occasional reference to the elevation drawings.
The combination of Inkscape and Roll20 works fairly well. Both have a bit of a learning curve. It can be annoying to get the maps right in Inkscape and it is time consuming. Roll20 can be quirky as well, and it takes time to learn how even the basic to mid-range features work.
Inkscape allows me to use layers while I'm drawing so if i want I can see various levels of the dungeon so that I can get things lined up correctly.
I export the layers as separate pngs for import into Roll20. In Roll20 they're separate maps. When moving from one level to another we just move the PC icons from one map to another.
I also occasionally draw a separate graphic image as an overlay on a map, so that an area can look one way one time and another way another time without having to make a whole new map.
All and all, it works well, although it is not without some quirks and tediousness.