DN and PF: Does the resubmission rule apply to PF and DN only? Does it apply to a PI or an organisation or a topic of application?

For DN it applies to the proposal as whole.

For PF, as of 2022, proposals involving the same beneficiary and individual researcher submitted to the previous call of MSCA Postdoctoral Fellowships under Horizon Europe and having received a score of less than 70% must not be resubmitted the following year.