Rubio has historically taken a hard line against Venezuela, Cuba and Nicaragua; he's usually been leading the vanguard on sanctions with those three countries in particular (has a lot of Latinos fro these countries in Florida). He's well versed in topics pertaining to Latin America (not sure about other areas of the world...doubtful). He may take a much harder line than what the previous Trump admin did with those three countries in particular.
When you look at Latin America there are several clusters of partnerships, mostly along the lines of ideology. Roughly looks like this (and yes there is a lot more nuance):
"Leftist" Populist authoritarians: Cuba, Venezuela, Nicaragua (Bolivia has been a part of that group in the past
Left leaning regimes: Mexico, Colombia, Chile, Honduras, Brasil
"Right" Populists: Argentina, El Salvador
Middle of the Road: Costa Rica, Panama, Uruguay, DR?, Ecuador?, Peru?