I just want to correct a minor thing. Español castellano is actually spaniard Spanish. The name originates from from castile iirc but it's mostly from the central and northern parts of Spain. As far as I'm aware we've always just called Spanish in Mexico, Mexican Spanish when in context to these sort of conversations.

As a native Spanish speaker I've always found portugués, Italiano, and French to a lesser extent easier to understand. Especially in the written form. Some Portugués dialects particularly I can fairly easily understand the spoken form of.