Planners and vendor accounts
No. An account holds one role. A vendor account opens the vendor dashboard; the checklist, budget, guest list and wedding page belong to couple accounts. If you are planning your own wedding, make a couple account with a different email.
No. Each account is one kind of account, and the dashboards are different tools.
If you are a vendor who is also getting married, sign up as a couple with another email address. If you are a planner who also runs a listed business, that is the one combination a single account can hold: see I am a planner. How do I get into a couple's dashboard?.