Hi Marco

<< I don't own any Mac pc/laptop....only Windows machines>>

Astropad will only pair with a mac, but Duet Display will work with
a PC desktop. It just may be less needed than for a laptop.

<<Which is this program you are referring to ?>>

Some worth considering are as follows:

• Affinity photo
• Concepts
• Procreate
• Graphic https://appsto.re/de/bM8Pv.i
• iDesign
• Protosketch
• Pixelmator https://appsto.re/gb/lUBh3.i
• Umake

Have a look at youtube video reviews
and when you get iPadPro, download trials
and have a play around...

And have fun!
James