I got a similar problem but with WD15 dock. I got no dGPU and original PSU shipped with laptop was 90W. I bought a dock with 130W and guess what? Bios reports the PSU is too weak. I ordered 180W for it and hope that I won't need to buy a 4th PSU 240W for this bleeping docking station. I don't get it completely...
My reseller quoted be $109 for a 240w power adapter. It's ridiculous that these TB16s want so much power, but doesn't actually need it to run 1080p screens and charge a 14" laptop.
I've run the TB16s on 130w and other than it yelling at me constantly about being under powered it works fine. Battery charges, no throttling, etc.
Confirmed that this USB issue is still a problem with a brand new TB16 dock using a 240w power supply, with a fully updated laptop BIOS, full updated laptop drivers, and TB3 drivers and TB16 firmware. It was actually quite a process to make sure absolutely everything was updated, as some things didn't show up on Dell Command Update, and during the Update process for the TB3 the progress bar simply stuck at a certain point for 20+ minutes and you didn't dare turn the thing off or you'd probably brick your TB16.
Plugged the $20 AmazonBasics wireless mouse back into the TB16 and it lags and skitters like crazy. Plug it directly into the laptop and it's fine. Similar experience with the keyboard.
Bottom line is that the USB ports on a brand new, fully updated TB16 dock on a brand new, fully updated 7490 or 5590 doesn't work reliably enough to be useful. I suggest using a USB hub and plugging that into your laptop and bypassing the TB16.
It's a garbage fix for an expensive dock that draws too much power and I'd love to hear someone, anyone from Dell comment on this.
I've the same problem without docking station but with a Hub USB. For me the problem not is the powersupply, but the simultanely use of USB, during the transfe of data the transferate isn't costantly and the mouse and keyboard show the problem.
Disabling C-states on a laptop will most likely diminish your battery capacity. I haven't tried this fix with my TB16s but I don't think it's a trade off my users would be willing to make.
I've had luck with alternate docks and posted my experience with one of them here: