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

Yes

The word "tão" is identical in meaning, grammar, and spelling in both Brazilian and European Portuguese. The only difference is in pronunciation. In Brazilian Portuguese, the nasalized vowel is typically more open and the syllable is pronounced with more resonance and a melodic quality. In European Portuguese, the pronunciation tends to be more closed, shorter, and more subtle, with less emphasis on the nasal vowel.

Brazilian Portuguese

1. Ela é tão inteligente! (She is so intelligent!)
2. O dia está tão quente hoje. (The day is so hot today.)
3. Você fala tão rápido. (You speak so fast.)
4. O filme foi tão legal! (The movie was so cool!)
5. Eu não sabia que era tão tarde. (I didn't know it was so late.)

European Portuguese

1. Ela é tão inteligente! (She is so intelligent!)
2. O dia está tão quente hoje. (The day is so hot today.)
3. Tu falas tão rápido. (You speak so fast.)
4. O filme foi tão fixe! (The movie was so cool!)
5. Eu não sabia que era tão tarde. (I didn't know it was so late.)