Hello again,
In my experience, large files with few line ends (like minified _javascript_ files) tend to lag more. Sometimes I just use vim for these kind of files or, depending on what I want to do, grep or sed in order to avoid opening it in Emacs. But that should be a rare case rather than the rule.
I like to think of Emacs as a code editor (mostly) which works great for development, but not necessarily for debugging.
Byte compiling your major modes may speed up processing, but I don't think of it as a general performance solution. This "tip" should apply only for custom installs because the default/built-in ones are already compiled.
In case you can share the file that you have trouble with I will gladly try it on my system.