Please, do not forget that when you change your tables in an incompatible way, report (insight) executions may start fail e.g. because missing column.
That is why it makes sense to re-scan as soon as possible and fix mappings between LDM and PDM. The rest (metrics, insights, ...) stays the same, that's the benefit of having LDM on top of PDM.
Hint: even when you move a column to a different table, there is no need to update metrics/insights/... - you move corresponding label/fact to corresponding dataset in LDM and keep its ID, which is referenced from metrics/insights/...