I don't like the cut of the crossfader. Can I adjust it?

Yes.
You can adjust the crossfader curve from the app settings as follows.

[WeDJ for iPhone]
Tap Gear icon > [Details] and select it in [Crossfader Curve].

[WeDJ for iPhone]
Tap Gear icon > [General] and select it in [Crossfader Curve].

[djay]
Tap djay icon > Gear icon > [Mixer] and select it in [Crossfader Curve].

[edjing Mix]
Tap Gear icon > [Audio settings] and select it in [Crossfader curves].

[rekordbox]
You can adjust crossfader curve in rekordbox [Preferences]> [Controller]> [Mixer].

*Crossfader curve affects the way the sound changes when you slide the crossfader. You can adjust it to suit your preference when scratching or mixing.