HTC 10 Setup

[GQ man]

Hi folks so ive just picked up a HTC 10 mainly because of its onbaord internal DAC, now im a Newbie to all of this but wish to know 
#1 why does this app make music sound the best with phones with dedicated DAC'S compared to other music players etc ?
#2 what settings in the menus do i check or uncheck for best quality playback etc

thx in advance.