With regards to the 27% rule, this is a special tax rate reserved for expats (non-Danes) who earn over the minimum threshold per month of 72,500 DKK and have not had the ruling before. The ruling effectively caps your tax at 27% for up to 7 years. There is an application process that must be done to try and claim this expat incentive, however, this can be done by the employer (People 2.0) so as to save the candidate the admin. The application process time is the frustrating part, as it takes approx. 6-8 months to have an application approved at the moment.
Once approved, should the candidate decide to leave Denmark, they can freeze the remaining years of their ruling and then reinstate it, with the remaining years, should they return to Denmark in the future.