Is the word nisto the same in Brazilian and European Portuguese?

No

The difference between the two variants lies in typical usage. In Brazil, "nisto" is used almost exclusively for things that are physically immediate (something you are touching or pointing to) or something that is about to be introduced in a sentence. For any topic, idea, or event that has already been mentioned in a conversation, Brazilians much more naturally use "nisso." In Portugal, "nisto" is used much more broadly to refer to the subject of the current discussion, even if that subject was introduced earlier in the conversation.

Brazilian Examples (using "nisto" for physical or immediate objects):

1. Coloque a chave nisto. (Put the key in this.)
2. Preste atenção nisto aqui. (Pay attention to this here.)
3. O que há nisto? (What is in this?)
4. Não coloque nada nisto. (Don't put anything in this.)
5. Eu acredito nisto (pointing to a physical object). (I believe in this.)

Portuguese Examples (using "nisto" for discourse and previously mentioned topics):

1. Não quero falar nisto. (I don't want to talk about this.)
2. O que pensas nisto? (What do you think about this?)
3. Não posso acreditar nisto! (I can't believe this!)
4. Nisto, não há dúvida. (In this, there is no doubt.)
5. Repara nisto. (Look at this/Pay attention to this — referring to a topic being discussed.)