Please take this out of kindness, I am simply giving my advice!
I am always excited for people interested in camming because I love what I do and I really think the adult industry needs to grow out of the awful stereotype it has. It is not bad work and no one should be treated differently for it.
With that said, I understand when you first start out being its only natural to be worried about people recognizing you; but the big thing I worry about here is that you are feeling so conservative and wanting to hide it so harshly.
To me, people like this shouldn't get into the industry. Simply put, it's not for you.
When you get into camming or any form of adult entertainment work, but especially things that revolve around being online: it is inevitable that you will be found out eventually. You can take all the precautions, be extra careful and watch your steps meticulously, but in the end nothing can stop things from getting out there online. People will record your shows, screenshot certain parts of your streams and post things about you which is fine for publicity in the beginning. Your image will get leaked constantly by fans and its just something that has to be accepted as there is no way to keep it from happening. These people are not in your control and half the time you won't even know they are doing it until its most likely too late. I cannot tell you how many times I have found recordings of my shows, leaked photos, and the sort. Its a big annoyance for a cam girl but its also a big part of the cons.
Camming is all about self-promotion and if your too cautious and don't put yourself out there then you won't make it. You can't worry about who finds out about it and being this way can also be somewhat dangerous. Remember, this work can bring out the worst in people and with that sometimes fans can get weird or even become an internet stalker. I won't go too far into that side of it though. Just please put together the pros and cons for yourself and really be sure you are okay with the work even if one day people may figure out who you are.
TL;DR - My overall advice:
1. How do I conceal my identity?
In simplistic terms, you become a new person. Choose an alias and stick to it, use a fake name, age and birthdate. Obviously never give out your address or number. Blocking certain states can help some but not 100%. Covering tattoos seems to be going a bit far in my opinion only because that can easily wear off when you stream due to sweating, rubbing, and especially bath shows or shower shows. Its a bit impractical. Just rock them! Wigs can work but are easy to tangle and be ready for comments about them - I get them all the time from guys who are unaware of cosplay. At the end of the day though all you really can do is just stick to your character.
2. What are the best sites to get started with?
I started four years ago on MFC, its a good site but the CamScore is a hinderance. It makes the work very competitive, so if you choose to start with them make sure to work you cute booty off as much as possible to get as many regulars and tips as possible so that your CamScore is as high as possible because once that "New Model" tag wears off, most of your attention will split with it and your activity within your room will see a significant drop due to the CS. Honestly I am hearing a lot of good words coming from PornHub and I think I might go give that a go next.
3. I was looking into having my partner join me, any pointers for getting into couples cam?
The only site that couples ever seem to make a profit on is Chaturbate and even then I personally think solo cams get better attention and views. I don't know why but unless its girl on girl cameo type of streams then the partner aspect looses the interest of a good chunk of viewers.
4. What are the boundaries in cam?
Boundaries can vary site to site but you can always read up on their policies and list of taboo's on their sites, its easy to access information. The main restrictions I see on all sites however are things like bodily fluids (blood, urine, vomit, etc), DDLG or anything that involves age play (Even wearing pigtails believe it or not), and obvious things like having people or "models" in your room that are not registered.
5. What are some good ways to stand out?
Make your room a comfortable place to be and don't always focus on the masturbating/sex aspect. Be yourself or stick to the character you have made and get involved in your room conversation. Regulars will bring in most of your funds so treat them like gold. Come up with fun games like drawing things you could do out of a hat, invest in a spin board, do raffles, and most importantly have fun. Your engagement and energy is influential, so if you want an active hyped room then be so yourself. A good background set up and overall aesthetic are also great ways to get people drawn in!
Hope this helps, and again I am not trying to steer you away what so ever! I simply see all too often models that join then drop it all after a year or even less because it turns out to be too much work or just not something they enjoy. This work and what you do, what goes out there isn't something to do just for a short spontaneous moment in your life. If you're going to do it be sure and have fun with it.
Best of luck and lots of love!