I would think yes, if you can accept the performance hit. Always have to be careful of what files you share between guest and host. Even browsing as another MacOS user would offer much isolation from your main account if you make your main files unreadable by the rest of the system.

Generally speaking, yes, though if you are that concerned about browser exploitation then a more practical mitigation is to browse untrusted sites with JavaScript disabled.

This is what I do.