I've used a mooncup for almost 20 years. There are guides online which show the differences between types of cups.
You only need one and sterilize it between uses. I boil mine. Some people use sterilizing fluid/tablets. I've had my current one for 8 years.
In my experience, they don't "need" changing in the same way as tampons or pads so it's more about when you want to. I tend to only change it at home but that's because I'm worried about dropping it down a toilet! If you don't change it enough though, they do smell.
I've never had to use pads as well but I don't have a heavy flow. If you are getting lots of leaks it might be that you don't have one that fits properly.
They are a little fiddly to begin with. You have to fold it to put into in which is a knack. To remove it, you pull it out. It has a "stem" which you need to pull but you also need to use a finger to break the seal sometimes and if you are likely to be full you have to hold it as well. It's not as difficult as it sounds though.
If it gets miscoloured or smelly, leave it in sunlight for a few days.
It's not easy to do but I put it in too high up once. It hurt. Lots! If it's too low, it can rub you. Some come with long stems which need trimming to the right length for you.
I read that tampons increase period pain because they draw blood etc into them which can cause muscles to spasm. I definately experienced less period pain since moving to a mooncup.
The blood doesn't congeal although obviously period blood can have thicker bits in it and it can be a bit... mucusy.