Is the D-RTK 2 High Precisoin GNSS mobile station required if I have a internet based VRS?
If I am required to use teh D-RTK 2 station, where do I place it in relation to my project, pilot and drone?

If I end up using PPK, does the drone come with processing software?

no base station is required if you can connect to an NTRIP server.  No it doesn't come with PPK software. You can use RTKlib, which is open source and free. Beware PPK is not easy or quick.

Hi you may use TOPOSETTER software for PPK processing. It is easy to use https://topodrone.org/product/so ... ing/toposetter-2-0/

@Skyveyor's answer is correct. No need for D-RTK 2 if you're using NTRIP. If you do use it, it should be placed on a position for which you have cm-accuracy coordinates in or as near as possible to your survey area. You will need to enter the coordinates into the app in WGS84 Lat/Lon Decimal Degrees with the Ellipsoid height including the APC height in meters.

No software of any kind comes with the P4 RTK other than GS RTK Pro, which has no processing functionality.

PPK is no picnic but can be done with a variety of paid and free software & workflows.