Setting up LLC in Wyoming Via Firstbase io

Hi,

I have decided to go forward with registering an LLC in Wyoming using Firstbase.io and I have 3 particular questions. P.S. I have a web & mobile app development studio.

1. My clients are spread over all the US states, I have read that if you are a registered LLC in Wyoming and you conduct business of any kind (even if its online advertising) in any other state you need to have registered your business with that state. Is this true? because this will be hella inconvenient.

2. Can I register with a mail forwarding service in NYC or Los Angeles and have that as my registered address for banking or does it have to be Wyoming.

3. I have been hearing about Anytimemailbox (which is what Firstbase.io recommends) but whatever I have read online it indicated that they are very unresponsive and difficult to work with. I primarily need the mail service provider to forward me the debit card issued by the bank. Does anyone have any recommendation on reliable mail forwarding services?

Lastly, what am I really missing by not incorporating as a C Corporation. I don't think I will ever need to issue stocks because the main purpose of me registering a LLC in the US is to allow me to open a bank account (Mercury I'm thinking) and allow my clients to make direct deposits because we are starting to get bigger projects now and PayPal/international bank transfer fees is not gonna suffice for us.