Sound Quality and Verizon FIOS Fibre Optic Internet

I am hearing a compromise in clarity when running my audio stream using the router provided by Frontier, which is Verizon FIOS (fibre). I’ve tested this, comparing the stream running from my iPhone connected using the hotspot feature to my MacBook Air on my T-Mobile data plan. The stream running this way is clearer and more resolved. It is more noticeable in my circumstance because the setup is very resolving. I here the same thing when listening on my iPhone with headphones (either wired or wireless EarPods). Switching from the stream run over WiFi then over T-Mobile LTE there is an instant improvement in resolution and absolute clarity: Any opinions, reasons why, similar experiences and suggestions are welcome and appreciated.

Best,
AK