I like seaweed. Mostly I like it whizzed up into pulp, spread out on sheets and dried.....especially good if done in the oven and it sort of roasts it. It becomes a crispy munchy.
I do like it added to my soup too, but usually that's just really thin stuff cut up into pieces or whole leaves dried and then crunched. It's amazing to watch it 'live' again as it writhes in the hot water while it's softening.
The whole leaves can be used to wrap fillings like cabbage or vine leaves, but a lot of our native seaweeds are pretty small stuff and pretty cheugh.
Sea lettuce, carrageen, purple laver and sugar kelp are good
As far as I know there are no poisonous seaweeds, just that sometimes the waters they're growing in are not healthy. Algal blooms for instance.
I am allergic to fish and shellfish, so I have to be careful with the seaweed. I have to really wash mine, but when I was little I loved that salty chewyness of the kelp stems straight from the sea.