GrapheneQuestion Well I'm ok with less convenience for more privacy security however having cellular data isn't really something I can feasibly do without sadly
Good sources for threat modeling:
It's good to start with a general approach to set your values and rules, and then work around them. You might figure that for example your location being trackable is okay, something you want to minimize or an absolute no-go. If it's something to minimize like you suggest, you could then find ways to use mobile internet without your phone, e.g. a mobile router that you can quickly turn on and off without compromising your phone's offline usability.
But this would be the detailed result after making a general guideline for yourself to follow.
GrapheneQuestion I know phones are inherently less private than desktop computers but is there a way to mediate it somewhat?
This is not necessarily true. I think you mean out of the box an Android or Apple phone sends more data about you because of how it's used and its capabilities and sensors. But compare a fresh install of GrapheneOS to a fresh install of Windows, MacOS or even Linux, you end up with a much more private experience on GrapheneOS.
This is due to the many privacy features such as contact scopes, storage scopes, mac randomization, sensor and internet toggle, sandboxing and many more.
A desktop OS has less sandboxing, less compartmentalization and less security and it's practically impossible to mitigate this by yourself. All have a crucial effect on your privacy. At least that's how I understand the matter (I'm not speaking for GOS and also please don't trust random strangers on the internet ;)).
So regarding your question: Without knowledge, you can't really do much for your privacy on a mobile or desktop OS, except use GOS as much as possible and trust that the internet people are correct by saying it gives you more privacy by default.
Privacy is a very subjective matter, as it's not about sharing as little as possible, but rather about controlling your data and share precisely what you want to share. For me, great privacy is when I share all the healthy lifestyle information with my medical insurance company to keep my rates low.I can do that by paying with cc for the good stuff and actively reporting my visits to the doctors for routine checkups. I really want to conceal all information that they consider unhealthy though. So I buy candy with cash or hide my underwhelming step count per day by not using a smartwatch or fitness band with online accounts but rather the PineTime offline.
You see how deep this rabbit hole can go, so my last advice is: Take it slowly. Make a general and small set of rules for yourself and work from there. Over many years, you will improve, adapt and also develop yourself into a nice lifestyle that matches your personal privacy ideals. Don't rush it, and don't fall for general advice on what apps or settings (not) to use. Privacy is individual and complex, but you'll get the hang of it over time.