I've been using some form of tiling manager for 4+ years now (herbstluftwm at the moment, though with stints using i3, awesome, dwm, bspwm and xmonad) and I've never had a problem with lines over 80 characters. I tend to use small font sizes, but I can't recall ever getting into a situation where 100 character lines were an issue. I can't recall any of the mangers I've used having a key combo to open up an 80 character wide terminal, though I could be forgetting.
Do you find herbstluftwm to be better than i3? If so, in which way? I've been using i3 for a few years now, I'm VERY happy with it and I'm curious if/how [0] some other tiling wm can be better.
I've been a huge fan of herbstluft since I started using it. Herbstluft's 'frames' definitely take a little while to adjust to and it took a few days to figure out how to fit hlwm's tools to my normal workflow, but I find the manual partition/automatic tiling within partitions system to be my favorite paradigm by far.