I would consider Herbert at 5, but I wouldn't trade up, and I'd rather trade down from 5 if I can't get Tua. For Miami, those are my two favorite scenarios - Tua or trade down.
I'd prefer Tua, but maybe Washington is smarter than we think, and he's not an option. If Jacksonville wants to move up from 9 to 5 for Herbert, I'd target their 2021 1st, which would likely be a Top 10 and maybe a Top 5 pick. If not Tua, the best QB option imo would be Justin Fields, so I'd want to position myself to have a shot at him.
The more I go over these QB's, the more I feel the gap between Herbert and Hurts is significantly smaller than the projected cost. So, with Tua not an option, I'd want to target Hurts in 2020 and Fields in 2021. Hurts should be there at 18 and probably 26, so Miami would be able to use that (hypothetical) 9th pick on Wills, Wirfs, or Thomas.
If I thought there was real space between Herbert and Hurts, I'd say just draft Herbert at 5, and I still wouldn't hate it, but I think you maximize value and opportunity to land a stud QB with the aforementioned, trade-down scenario.