Hiya,
Belts: a 5cm/2" wide leather belt is perfectly ok if it’s brown (ok) or red (best). You can hang your pouches and jingly stuff, and then obscure the belt with a sash over the top of it. Or do as Saiph does, wrap the sash/scarf around your waist, then put your belt over it (a little like a very wide obi with the narrower belt atop it).
Singing and music: I’m not a singer or a musician, but I still sing along and I beat my drum when it seems to fit… so far, no one’s complained. If it was that bad, they’d probably pay you to stop (we are Freeborn, we’re generally honest that way).
When you approach a Freeborn tent or camp, ask ‘How much?’ to sit by their fire, you can also mention that you’re ‘New to Anvil’ to get assistance if something confuses you.
If you’re a physick, you don’t need any tools or physreps (other than what’s needed for the apothecary potion making) in order to use your physick skill. Some people do not like to be touched, so you can still roleplay physick with just coins or bells on a cord that you shake over the patient, or whatever, if space and weight are premiums in your travel. I know of one physick who scolds the patient’s wounds into healing. Also, you can shadow the more experienced physicks at the Anvil Hospital Tent (it’s placed close to the Sentinel Gate) who can show you how they heal people coming back from skirmishes or the battles.
If you want to experience a battle, you could NPC (basic and drab tunic and trousers, and ankle-supporting boots) as a water carrier, you get to see a battle without putting your character at risk. A water carrier basically gives water to the monsters, your NPC might receive some scolding, that’s part of the play. Bonus is that you don’t have to wear a mask, which for some folks, can induce panic attacks. Also, armour that doesn’t properly fit you is a health hazard, and borrowing another’s armour could cause difficulty.
If you wear spectacles/eyeglasses, you’ll want to have them on a cord that if they fall off your face, won’t get as lost. Having a second/spare pair is also wise.
Jewellery: my Freeborn wears some colourful little crochet pouches, strings of wood beads, and plain stuff, I don’t wear any metal necklaces on show (I do wear my military dog tags for emergency reasons, but they’re tucked into my clothes). I do wear a ring or two, and mostly go silly with glass bead bracelets and brass cuffs around my wrists. You could also wear bells on a cord around your ankles. I also wear a faux nose ring and gauged ear plugs for extra bling.
Fingernails and cosmetics: avoid the metallic (gold, silver, copper, bronze, brass) ones, and avoid black, as those are all lineage. (Black fingernails are part of the draughir physrep) However, if they’re sparkly red or orange? You’d be ok. Avoid black, gray, red and orange eye-shadow, as someone might think you’re draughir. Avoid spirals or tendril-like facial/body embellishments, as they might be confused with either lineage or the Navarr. However, if you want to, knock yourself out with facial ‘scars’ via collodion.
Overall, your costume idea looks splendid. I would recommend sleeves that you can fold/roll up above your elbows, E2, E3, and E4 can be quite warm for Britain. You might want to consider a few extra light/thin layers for the upper body. Voile and lawn cottons for making extra bits from can be a boon for heat/cold management. Also, consider ‘Anvil Cut’ for your lower half garments, ie end at the bottom of your calf, or closer to the knee… mud can happen, and if you don’t have extra pantaloons or bottom garments, you might feel miserable when they get soggy and sodden. I bring a pair of wellies and a pair of tactical boots. I tuck my pantaloons into the wellies, but I blouse my pantaloons over the tactical boots to obscure the boots. “Costume ends at the ankle.”
Archetypes, sadly, the Brass Coast doesn’t have a devoted healer archetype. Saying that, you can completely forgo any archetype at all. (I play a physick too, and it took me three events to settle with ‘Corsair’ even though it still doesn’t fit, it grants a bit more game options.)