So, since no one found the solution yet, I’ll explain how I did it, which is I think the way to go:
- Create a new landscape (once you created it you won't be able to increase or decrease it's resolution I think, or at least I didn't find a way to do so.
- In the Manage tab you can see several settings, the ones we're interested in are the Scale, Section Size and Number of components.
- If you increase the Section Size or the Number of components and then you reduce the Scale, you will end up with a higher definition terrain, that can be sculpted and textured properly.
I don't know if this is the proper way to do this, anyway there is no documentation on this anywhere. Hope this can help someone.
Have a lovely day.