Shalom, regarding Nori/seaweed with a hechsher.
Is it recommended or needed to check nori before consumption?
If yes, do you know where we can find a reliable guide to check nori?
If the nori has a reliable hechsher, you don’t have to check it, as this is included in the hechsher.
I can’t not advise you how to check them, as there are a number of Kashrus agencies, such as the Crc in chicago, and the London Bais Din who recommend not to buy nori that does not have a reliable hechsher. here are links to the two sites.
When you get to the page type in nori.