Whether or not to use macOS resolution scaling is a matter of personal preference, but I would recommend against manual setting of Windows resolution. Some people will try to fix that, setting the 'correct' 2880x1800 resolution in Display properties in Windows, just to find out that the display becomes fuzzy and out of focus due to double scaling. Parallels in turn will set Windows to that logical 3840x2400 resolution, causing text to be a bit small. Newer MBPs come configured to what was called 'More space' mode before: a 15' with 2880x1800 panel is set 3840x2400 by default. The matters are complicated by macOS resolution scaling, the thing you can set using macOS display properties. The above assumes that resolution in macOS matches display physical resolution.

Moreover, per-display DPI support is even more complicated. In this mode you have more control over scaling factor, Windows applications, however, are still required to fully support DPI scaling. All VM displays are set to native resolution, Windows adjusts DPI scaling automatically per-display which can be overridden (ex.

Parallels desktop windows 10 resolution