Project Budget Type and Financial Plan Type

We have been using multiple Project Budget Types and updating budgets via Project Costing. We are implementing Project Management and as such, are converting all Budget Types to Plan Types.

Questions:

1. For a given project, can we continue to have a budget type for a project and a plan type for the same project or can there only be one or the other? For example, can we have a budget type which is updated in Costing and reflects an annual budget value, and have a plan type which reflects the forecast and is updated in Proj Mgmt? (budget updated by accounting and forecast updated by engineering)