I believe your bonus melee unit and extra trade route only occurs when you found the city on a continent other than your capitol’s. Those bonuses are a little bit of just icing on the cake. On a huge map with continents and islands, you can get on all the continents but it takes a lot of effort. Meanwhile you could just win the game with a science victory or something.
However, if you practice building a strong economy as early as possible and you don’t try to do very wide around your capitol, you can send a settler to a different continent and by the time the city grows to size 2, you can just buy a settler and expand. That is the real key to England (my theory). Get some colonies going by having a strong economy and put in the policy cards to benefit them.
I have not been able to do this reliably, but being able to buy an industrial zone as the first district in your colony, and if it is after you have power plants, you can buy the oil or nuclear power plant when it is available to provide extra production to city centers in range might help develop a colony more quickly.
If you can a city founded on all continents and grow a colony there then that is very good play. I think she definitely better on a huge map and while standard speed is fine, on deity, you are very pressed for time. You science fast to get on the ocean but you need money too and a lot of it. To that end, you get iron and coal at an increased rate. Find them and any resource and luxury quicky and get some money coming in. If you can, build up your treasury for your colony so you can buy city buildings and perhaps a district.
It all about colony building and your red coats can help hold them, but if the cities are coastal and many will be your fleet can get there quickly to defend them or retake them. Frigates are great at clearing out barbs along the coast when landing a settler and escort.
Your unique harbors are cheaper and there is a pantheon that reduces the first district built in a city by 25 percent if you plan on building the first ones. It is hard to buy everything with gold but every lighthouse gives a trade route if there isn’t already a market there.
The unique harbors give 4 loyalty so they can help hold a city along with cards and governance. Victor can give 12 by himself.
Edit: I also wanted to add, culture can also be very helpful to get to Mercantilism faster. Mercantilism will give you the Sea Dog, normally a privateer. The good thing about these boats for exploration is that as raiders they can collect the tribal villages on coasts. On a huge map, the Sea Dog and cartography is a strategy for ocean exploration.
