Spouse joining me on National D-Visa & Residence Permit questions

I was recently approved for my D-Visa for self-employment and shall have my residence registered as soon as possible.

I have read some mixed things regarding when I would be provided with a residence permit; in some places it suggests that the visa would be converted to a residence permit 6 weeks before the visa runs out, in other places it suggests that I can't work without the residence permit first. Does anybody have further information regarding this?

If my spouse were to wish to stay and work in Germany through a family reunification visa, would I explicitly require a residence permit to do so, or would the National D-Visa suffice in this case?

Thank you ever so much for your input.