Looking for some way to map out previously travelled areas of a dungeon, with dynamic lighting on?

I tried LightCrumb which is essentially want I wanted, but adding 20 other light sources really lags the engine. Is there something similiar? Maybe that combines a fog of war or something?

There isn't an interface to Fog of War from the API. The best you could manage would be to reimplement it with drawings, but it would block the GM and the players from seeing.  I could see duplicating the DL lines to the GM layer to give the outlines of things, and possibly doing the same with the map layer graphics (provided they aren't from the marketplace), but that's still a sorry substitute and would be an extremely ambitious script.  In the end, it likely wouldn't be any more performant than the LightCrumbs.

BTW: Lightcrumb has an option to set bigger distances between crumbs. Turn off "inherit light" settings and set the drop interval to a higher number. Play around with the options to see if you can get it to drop fewer torches.

I drop manual light crumbs. You can drop far fewer if you carefully place them to minimize sight blockage.