I have a travel router with OpenWRT running on a Raspberry Pi 4. I would like to know the power consumption of the device and everything attached to it (Wi-Fi Nic, fan, etc) so I can determine the required power supplies. I would like to power from Thunderbolt 3 port on my laptop when I'm in public, my car's usb c port in the car, which power adaptors (usb c bricks) to bring with me, etc. As a second question, if I power it from a source that doesn't provide enough power, can this break the pi?
Get something like e.g. https://www.aliexpress.com/item/1005001527372935.html
There are also plenty of USB-C power meters, but they tend to be a bit more expensive. I have a Rui-Deng TC66, which is a pretty nice device all in all, though I wish it had a little bit bigger display and buttons -- it's quite fiddly to use such a tiny device. There's also the Avhzy-one, but I don't have that and can't say much about it personally.
You can easily find plenty of other options on eBay, Amazon or Aliexpress.
No, but if the Pi isn't getting enough juice, you might corrupt the filesystem and need to reinstall.
Doesn’t a Pi4 draw 3A just by hardware design.
No, 3A is the suggested power-supply. The Pi4 draws something around 1.8A when all cores are under load, the rest is for any peripherals and such.