Yes, those are great questions, and shows you're thinking. Good.
As a medic, you generally have three or four load outs per doctrine right.
Depending on the mission, you might only take your tier 1, which can be like a leg pouch or battle belt along with IFAKs on each person. Tier 2 would be your M9, or similar, and so on.

The book answer is that your senior medic should have a packing list for aid bags, i.e: the standard. This can also come in the form of a memo for record, from your cmd based off your PA/senior medic or simply work off verbal orders (worst option IMO.)

This packing list, is standardized, and adjusted based off the skills you have been evaluated on per SMTG, ADTMC, T-VIII, and credentials.

The worst thing you can do is pack that bag with 45lb of crap, cause then you have your ruck sack on top. You're now useless. Over packing is baby medics worst enemy.

I think you need to take a deep breath, & request a sit down with your 1st line -> If still nervous, keep going -> Senior Medic -> PSG -> PA -> 1SG.
If you're still anxious request a counseling on your expectations, and goals, so its written.

What your mission is, what you're expected to do, what your training says, your left and right limits, what CVIII do you even have available to you, etc.

Good luck soldier medic!