Ultimately, only you know what sounds “best” (to you). Don’t be afraid to dislike settings that another individual claims are  “great”.

I suggest that you search for “loudness compensation” and study its purpose. Since the loudness compensation schemes incorporated in hardware are only approximations and each individual’s hearing and room is unique, the function does not work well for everyone.

Your room layout and acoustics, hard/soft furnishings will all play into the equation. As @buzz says, let your ears decide what’s best. 
Personally, I do tend to play a bit with the settings for my kit, depending on the genre of music I’m playing, the volume I’m listening at, and my mood at the time! 

Thank you so much for your help.

Kind regards.

I’d suggest setting everything to flat and running Trueplay. Listen to it for a few hours to get your ears used to the sound, then try tweaking things.

I’ve found very different settings sound best to me in different rooms.

The Loudness option does sound good to my ears at lower volumes but when trying to listen without disturbing others it works best off. Turning the Sub off in that situation also helps.