With the recent onset of remoter workers-employees working from home has increased the need to ensure the quality of service so that cllers are provided provide the same level of service as the would get at the office. The biggest problem is the fact home workers will different internet providers, different modem/routers and varing speeds and latency levels. controlling these variables is difficult, but there are things you can do. The equipment from the various telcos differs greatly and learning or requesting specific routers/ modems will allow you to know their optimum settings for VoIP. If you understand the various routers you will able to set things like QoS so the voice calls always the required bandwidth even if someone is downloading a movie! Disabling sip ALG almost always improves VoIP call, SIP ALG was designed to help with VoIP but most manufacture failed miserabley making disabling it manditory.
If budget allows provided seperated internet connections at home, buy using a independant ISP, they are more flexible and can assist with providing you a more standarized router options.