Para estudar certificação, vale a pena buscar materiais externos ou somente o Trailhead é suficiente para tirar uma nota boa na certificação?

Hello @Marcos Gomes

Normally if you follow the Trailhead preparation trailmixes (suggested in each certification exam guide) and you have played a bit in a real instance on the same related topics, you should be pretty ready to take the certification exam. Naturally, real life like project / experience, dealing with the same topic, is a real bonus to help you get pass the exam. 

Good luck for it ! 

Eric