RE: TB16 constant flicker at 60hz (XPS13 & 4K Dell P2715Q)
Same thing for me. I run two 4k ASUS MG28UQ with the TB16 and a Dell XPS15 9550.
The ASUS monitors flicker off and on randomly and occasionaly drop out completely. When one drops out I haven't found a reliable way to bring it back online - turn off then on, reboot the laptop, reboot the TB16 etc all typically fail (but randomly occasionally succeed).
Sometimes one of the monitors will come back on, but not really - Windows will make its little noises as the device is "plugged in" - the screen will stay black - but it'll be visible in the Intel or Win10 display settings, but with no attributes - i.e. the resolution, orientation etc will show as empty fields and the picture of the monitor that shows in either of those two places will be a tiny square - a fraction of the size of the other two monitors.
Oh, and all of the USB ports in the TB16 are flaky. Sometimes they work and sometimes they don't. They'll all be offline and then randomly a couple of them might start working or perhaps all of them.
Even when they're working they're worthless for using a mouse - I have to run the mouse from one of the two ports on the laptop itself. Running the mouse from one of the TB16 ports results in a wide spectrum of performance - occasionally working "normally", then degenerating into partially working (the mouse skips all over the screen - working / not working / working / not working / working ...), and then periodically it just flat out stops working - even if the paired port for example (with the keyboard in it) still seems to be working fine.
Yes, all the bios, thunderbolt, etc drivers are current.
I could've just bought a thunderbolt-to-2xDP adapter, plus a 10-way USB 3 hub and (presumably) I'd have a functioning system without the cost and b.s. of dealing with these Dell TB16 docks. I run an identical setup at home and at the office - same laptop but duplicated monitors + duplicated TB16 at each place. Same behaviour in both environments. It's a MS mouse + keyboard at the office and Logitech mouse + keyboard at home and same behavior from each of the mice, so is not a mouse problem.