Gaming and warzone/CoD in general packet burst

I've done everything I could. Replaced the modem, gotten a separate router with SQM/QoS capabilities, called a tech out, there have been no answers. I pay $120 on my bill every month for 500mbs and nothing to show for it. It's the most frustrating thing to have around 30-50ms ping but still have lag stutters, packet burst symbol pop up, and faulty hit registration due to speed spikes. Who else is feeling this? I want to back to 150, but its even worst! Can't even play a game due to the heavy lag. Is there a fix? Cause everyone at cox seems to be dismissive and gives no real answers or solutions.