Will DC converter straight into 5V be okay with USB plugged in as well?

I'm using a 12v battery with solar power recharging to run an Arduino Uno and a water pump. I had read that the linear regulator in the Arduino might be a bit too inefficient and run too hot for me to permanently use this on a battery setup. So, I've added a buck switching DC-DC module to supply the 5V regulated directly into the Arduino 5V line i.e. not through VIN, so bypassing all the Arduino linear regulated supply. This gives all the efficiency of a buck and better than dropping to 7V and going through the VIN and using the linear regulator to drop the last two volts.

I would like to read the Serial output from the Arduino while debugging, and maybe later using a Raspberry Pi to put the results of the sensors into a webpage hosted on the RPi.

Can USB still be hooked up to the Arduino, while battery powered? And same question especially as I have bypassed all the Arduino regulator electronics - I think it had a mosfet there protecting things like this.

I'm worried I'll fry my computer or my arduino if I plug in the USB. Will the USB power and the buck regulator fight each other?

Many thanks for the help.