I think some types of clean-ups, for example, imports, are pretty low cost, low risk and don't have much bearing on and it might be best to do them all at once. 

f-strings are also pretty simple but can be abused to the detriment of code around (for example, moving a string defined in a variable outside a function into the function just so it can have an f-string).

I think more general code clean-up, for example, removing list around iterators (e.g., list(map(f, i)) should be mostly avoided unless there is a compelling case to prefer the iterator for performance reasons.