I’ve always measured a tie at its widest point. A 4” tie is really, really wide in my opinion. I have a few and don’t wear them unless I’ve got some massive lapels on my jacket. I think 3.75” is kind of the upper limit, but even that’s kind of pushing it.
As for wearing a wider tie with a slimmer lapel, I think you can do it — but it’s a matter of degrees of difference. A 1” difference is going to look perhaps a bit out of place, but probably not as bad as a 3” tie on a 4” lapel.