I catch lobsters and crabs as a hobby, and this is something I started at a young age (5, small crabs).

I killed and cooked countless of those creatures.

There is absolutely no doubt that they experience pain and fear, like all animals and probably also many plants.

From my experience, I don't think they suffer that much when boiled alive, they die in less than two seconds, it is very quick because of their low volume and good thermal conductivity.

I think they suffer much more during transport.

Alas, like many seafood they deteriorate extremely quickly when dead. A lobster that has been dead for even one hour has a very different and unpleasant taste.