yes, I keep IE (or whatever it's called now) and Chrome in reserve in case Firefox plays up. I don't have bookmarks on them, they're just for emergency use.
I've installed lots of browsers but only keep three of them on my taskbar. I have desktop icons for the rest as I don't like the taskbar being too cluttered.
It is a bit pointless keeping Internet Explorer if you also have Edge. IE is legacy software and Edge does everything it does, only much better and faster, and is being constantly updated and optimised.
A browse could have any number of shortcuts in its bookmark manager. However, if it's not actually running, it will consume no resources (memory, processor cycles, screen writes etc) at all. Some applications are set to run when the operating system starts up, but browsers generally aren't.
This is why having one anti-virus package is good but more than one is bad.