After spending a few hours getting a new flow working correctly, I found that there is no option to set an event category for the 'Create Event (V4) and Update event V4' flow templates. I should be able to expect that all of the features and options available in the OWA version of Outlook would be available here.
Running through all of the available options, it looks like event categories and designating the event as a teams meeting are the only missing options. Please see my color-coded comparison.
Thanks for reading!
Color-coded differences of options between power-automate flows and OWA outlook calendar