The developer is overly modest about the power of MarkEdit.

I have a 200,000-page TXT file that I use to test document editors and tried it with MarkEdit. It's about half a gigabyte in size.

MarkEdit opens it in just a few seconds. Scrolling is easy. Line wrap is on and resizing the window is instantaneous. Very few document editors can do so. This is wonderful.

My testing is done on an M1 Mac Mini with 16 GB RAM.