I think the problem is not with colonizing other continents, but settling new cities post renaissance in general. People talk at length about how settling new cities is not a handicap in spite of science penalty (at least not after a handful of turns and hard-buying a library ) but what people seem to forget is discussing what these new cities actually benefit you, and most often the answer to that question will be: Nothing but trouble (for starters: Happiness and diplomatic relationships).
That is actually a very interesting proposition. This might make a great finisher benefit to the Exploration (or rather: Expansion) tree. Imo. this is a very neat way of coming around a number of balance issues with late-game new cities without breaking early-game new cities.
Yes?
Of course if you settle a new city later in the game you have to invest in it to grow it faster. Either get policies or tenets that help with food or hammers, run an internal trade route to them or outright buy buildings.