I have a NEXX XD1 helmet. Had it for some years now. I find the quality to be good, have had no issues with mine. I have the bluetooth installed as well. Sounds ok, not as good as my Schuberth C3 Pro but good enough. Not great if you are travelling and on the interstate and do not have a lot of wind protection. I love the features my helmet came with, drop down sun visor and modular in a way, I can remove the peak and they parts that replace so it is more streamlined and aerodynamic. I personally would not hesitate buying another NEXX helmet.
I have only tried contacting the company once when I was looking for a Canadian retailer of my helmet. They never replied, not even a canned "we got your email" response. So not sure how they would be with warranty or anything like that. Thankfully have not had any issues.