I think long lines are (were? [1] seems to be a new feature) a well known problem in emacs even without a custom config. There have been ways to work around this for awhile I think, but as far as I know emacs -Q isn't one of them.
oh that's neat, i didn't know about that! could help.
my ideal editor would never block, and use file-sized based approximations to allow scrolling to arbitrary locations w/o having to actually read the contents of the entire. things like syntax highlighting &c would be either strictly time-limited to not drop frames, or done in the background.
[1] https://www.gnu.org/software/emacs/manual/html_node/emacs/Lo...