Okay let me humbly point out a few: 1. Your MS Surface duo 2 support LDAC which is the hi-res codec that almost every android phone has since android 8.1 oreo. So invariably you need to enable that and potentially you should get much improved sound. Disabling LDAC could poasibly even default to SBC which can be poor 2. If you say it has good separation, and it sounds like the soundstage is good, then bass must be auffering from choice of eartips. Anything short of the perfect fit would mar the lower frequency by a great deal, and even other ranges by extension. The particular comply eartips may not fit your ear perfectly, byt you should get a better fit from one of the other 6 pairs.
To answer your points... 1) The Surface Duo 2 did list LDAC in the Developer settings, but I was not able to select it even when using earbuds that supported LDAC. 2) I did try the 6 pairs, and didn't get the seal I wanted. I have since switched them to SpinFit eartips and I get the seal and sound I want from them.
