That's an easy question to answer.

python -m pip is often advised over pip or /usr/bin/pip, because it uses the version of pip associated with that particular major+minor python install.

https://snarky.ca/why-you-should-use-python-m-pip/

Guilty as charged. Using the system pip in an environment that doesn't use the system python is a recipe for disaster.

I do it on Windows using the python executor py. So I'll run something like py -2 or py -3 or even py -3.8 to start the correct version of python when I'm not inside a venv.

Also the same goes for modules. Since I've installed youtube_dl in my global python 3 I'll always run it like py -3 -m youtube_dl and update it using py -3 -m pip install youtube-dl -U. Or to create a new python 2 venv (for whatever reason) py -2 -m virtualenv venv.

for a very long time (I don't use python as a daily driver, so not sure if it's still the case) guidance was to use `python -m pip` and if you tried to run `pip ...` it would explicitlytell you to run `python -m pip`. I regularly install python on clean systems and all of my scripts run `python -m pip`. Should I be changing?

You should always use this form if outside a virtualenv.

I do it all the time.