Just started up my new Moto 6g and same problem as with my 5g. Too hard to hear voice including when on speaker phone. With the 5g I added an app that helped the speaker phone issue but shortly thereafter broke the phone and went back to using my old Moto X 2nd gen. It worked great with no audio volume issues. There are multiple posts here at Republic and other sites so it seems to be a generic problem with these phones., I will submit a trouble ticket and see what Republic has to say about it.
As you have already began working with RW’s Support Team, I would suggest we hold off on community suggestions … as they will know more than the community this will avoid us sending you down a rabbit hole and hopefully they can provide you some answers.