Is there a 1 cable solution to connect 2 monitors in extended mode and charge a MacBook 15" at the same time?
You need a Thunderbolt 3 dock - many exist.  What you seem to be confused about is that they require a Thunderbolt 3 monitor - they don't. You can buy a simply cable to connect the Thunderbolt 3 port on the dock to the monitor via DisplayPort or mini-DisplayPort.

I'm using the OWC 12-port Thunderbolt 3 dock for attaching dual-monitors to the MacBook Pro while charging it at the same time. Monitors are both connected using mini-DisplayPort. This does not use MST as that is not supported by macOS. Nor does it use DisplayLink. It is all connected to the MacBook Pro with a single Thunderbolt 3 cable.

You can also use other Thunderbolt 3 docks such as the OWC 14-port Thunderbolt 3 dock, the Belkin Thunderbolt 3 Express Dock HD, the Caldigit TS3, the Elgato Thunderbolt 3 Pro Dock, and many others. They all provide 85 watts for charging and allow attaching two monitors.

It would seem that the docks you have tested earlier are USB-C docks. They require MST to be able to support dual-displays, or they use DisplayLink. MST is not supported on macOS, so that's only going to work if you run Windows on the MacBook Pro. DisplayLink is generally limited in performance compared to a native DisplayPort signal.