There is no noteworthy loss of productivity after some practice in my experience, except when comparing with languages like Python. But among languages I would consider for serious projects Rust is simply difficult to compete against. In the end you always pay the price and often knowing it upfront can help.

With prototyping it's a double-edged sword: it can be a bit more cumbersome to change types, but the same type-checks are helpful for pointing out details during refactoring. For me it helps keeping things simple at first, expanding types later on when needed is easy.