Definitely A

Woow. That's pricey Lucid is getting greedy ? I guess.

The grey clear ones are small size and white translucent ones are of medium size. The foam tips boost the bass and reduce the treble clarity a wee bit, which is not for me. It works well on andro as it tames the treble sparkle and makes bottom end slightly thick.

For me the stock silicon triple flange tips (small size) work the best. I feel the foam tip boost the bass a bit more. That said, If you are looking for foam tips check Symbio ( foam / hybrid) or KZ foam tips. The best would be to get it from Etymotic , I think its available in amzon

I dont prefer the cable type adapters as they add length and more weight to the stock one. Also it is easier to keep it plugged into the source or IEM itself. So I didn't search for the cable type.

if there no huge price difference, 4XR would definitely be better than 2XR and stock 3SR/XR.

It is a regular 3.5mm adapter . You can check on amazon or Aliexpress

+1 to this, get a ER3XR with 20 or 75ohm adapter which s much closer to ER4XR and costs few more bucks than ER2XR. its pretty good bang for buck.

Have been using ER4XR / ER2XR with Fiio Q5 / AM3B combo, it sounds wonderful.

Yes, it is worth the change. Even I could not bring myself to do it. My friend.helped me out though. I am no more thinking about selling them. In fact any local electronic repair guys could do it.

Obviously you need to open the Q5 - which itself is quite a task as it seems to fixed with some kind of super glue. the remove / de-solder the stock OPA1642 (3 nos) and then replace / solder them with OPA2156(3nos.). The 2156 would cost around $2-$3 / each + the manual work. This would void any...

Stock OPA1642 replaced by OPA2156, This makes the Q5 Sound even more neutral and amazing. It has bit more air and both ends have little more body / air if I may call it that.

try Fiio Q5 / Q5s with AM3 / AM5 module. They Sound very good. other option would be iFi Micro iDSD BL.

I currently use Fiio Q5 (modded) + Am3 / Am5 module with LG G7 as source and switch between Andro and ER2XR . For me its quite enjoyable. Sometimes I even use NX4 just as an amp paired with Q5 as DAC.