The weird characters on copied HTML text is a known unresolved issue. Meanwhile, the list of missing features in Edge and other browsers but which Firefox legacy ESR (prior to ver. 59.02 ) enabled include:
Multiple tab rows (not in any current browsers though possible in Quantum only with hacks)
Change tab width and other options the TabMixPlux extension enabled.
Colorful Tabs
Toggling Ctrl+Tab switch btwn most recently opened tabs (not in Chrome, Edge, and some others)
Session Manager with options comparable to Firefox legacy.
Stay-open bookmarks
Find bar tweak (retain find bar for all tabs)
Menu editor