Hey Matt,
Cheers for warm introduction, good to have you here and I'm sure you'll find what you're looking for.
You'd struggle to find anyone here with much self-confident with their voice, think it's just a thing - and it don't stop us - so don't let it stop you!
Etiquette is generally treat others as you'd like to be treated, we're an equal community so you can only expect to get what you're willing to give. There's nothing rigid to enforce that which is great, because it puts emphasis on relationships which leads to honesty and comfort in critique.
There are a few rules to help with smoother running (I.e. 1 finished song every 2 weeks) and you'll find them in a sticky thread at the top of whatever category you're in.
If you've demos to share I'd suggest heading over to Finished Songs, having a read of the rules there, leaving some friendly feedback for others and choosing one of yours to put up.
Looking forward to hearing off you, and hope you find what you're looking for!
All the Best,
Scott