Is this income taxed in Poland

My name is XXX, write you on behalf of Estonian company XXXXXXXX OÜ, I am the co-owner and board member, XXX national, XXXX resident. We have some employees here in Poland (including myself) and we want to pay remuneration for some work they've done and we want to make sure we are doing it right.

Situation: person is living in Poland; citizen of XXX or XXXX; Waiting for (or have already) karta pobytu (zezwolenie na pobyt i pracę albo zezwolenie-niebieska karta) with a local polish employer (not connected to our company).

The same person has a remote job for our Estonian company. XXX has a Contract for a Work with this person and wants to send remuneration to the person every month.

Should this person receive some additional work permit? Should this person perform any steps other than filling PIT-36 and PIT-ZG and paying 17% or 8,5% (if the work was creative) of tax from the remuneration?

Is the situation becoming different if this person is a citizen of the US and has a registered działalność gospodarcza in Poland with codes for teaching, but the work she has been done for us is not related to that, so we would prefer to pay her as a private person.