just in case, OWC Thunderbolt 3 to Dual DP [1] adapter work fine with two 4k@60Hz separate displays (with MBP15 2019).
And seems similar Thunderbolt3 -> Dual DP adapters also should works well. But I agree that is a big mess with that stuff, I brought lot of usb-c->hdmi adapters before found solution with works fine with 2 displays (some of those adapters only supports 30Hz, some can slow-down MBP performance dramatically with 2 displays).
[1] https://www.amazon.com/OWC-Thunderbolt-3-Dual-DisplayPort-Ad...