Download minimap_v1.0.0.zip, then in Blender go to Edit > Preferences > Add-ons > drop-down arrow > Install from Disk... and pick the zip (do not unzip it). Tick "Minimap". The map appears in the corner of the 3D Viewport right away.

The map is redrawn at most 10 times a second (you can change that), and heavy scenes get fewer refreshes on their own. In our 1,996-object demo valley a refresh took about 4 ms.

Yes, but with Cycles or EEVEE the map picture pauses so it doesn't restart your render. Your arrow, pins and cameras stay live, and the picture updates when you leave Rendered view.