Fortigate firewalls have a performance sla that you can setup between two wans. Allows you to track ping time, jitter and bandwidth. It’s one of the ways it test for fail over. I use it to keep my isp honest. Looking at you charter, bag of dicks they are.
Do you mind telling me area, service and cost? We have charter but it’s coax. I wasn’t aware they were rolling out fiber other than the enterprise, which we use at work and has been pretty good.
Until win10 becomes eol they are still a solid choice. There are tricks to get win11 to install on older cpus but that’s totally a call you have to weigh and make.
Look into a business account with ATT, which gives the added benefit of a fixed IP.
I use a pep link at work, solid device. Early adopter cost was high, we got one of the first 5g standalone modems on the market and spent a few grand. We also had to get a fancy antenna but it’s a solid system.