Moka pots are awesome! I used one as my coffee making daily driver for a while so hopefully I can answer your questions.
Definitely feel free to lift the lid when brewing. In fact, doing this to keep an eye on the brewing process is recommended. Just be sure to close it or remove the pot from heat before the water begins to boil.
You can use any beans you want! I prefer using darker beans in my moka pot and the lighter more delicate stuff in my aeropress, but definitely experiment with all beans to see what your favorite is. For the grind, I use the finest grind possible that won't clog the metal filter. If I remember correctly, this ends up being about a medium grind.
Safety wise it's hard to mess yourself up too badly because moka pots ship with a pressure release valve in the main chamber. Just make sure that you don't overfill the bottom half so the valve should just barely be exposed above the water.
Biggest tip I can give you is prevent the water from reaching a boil at all costs. Use low heat and keep the lid open so you can watch the coffee flow. Once the stream reaches a golden honey color, remove the pot from heat. It will continue to extract as the pressure is released, but it shouldn't boil. At this point, some people will even wrap the lower half of the pot with a cold towel to stop extraction immediately.
You'll find the flavor of the resulting coffee to be similar to the undiluted "Aeropresso" you get from an aeropress. There will likely be more sediment and a heavier mouthfeel than the aeropress due to the metal filter.
You can get different flavors out of the bean by altering your dose, grind, and temperature, just like with any other method. Experimentation is key! It's tricky to really dial in this method because there is a lot going on, but it can make some really tasty joe. Good luck!