If you play a 3 iron and hit it say 180, then your 4 wood you hit 220, there's a big gap that needs filling. That 200 mark might be better serviced by a hybrid, and even that could be a 2, 3 or 4 hybrid that doesn't matter, what matters is the loft and how you hit it.
As an example I have a 4 iron 23 degrees loft I hit about 180 - 190.
Recently dropped the 20 degree 3 iron as I wasn't get much more out of that. Replaced with a 4 Hybrid (22 degrees) which I hit 200 -210.
Then my 4W goes 230-250 (on a good day!).
You have to have a putter and the irons at least 5 - 9 plus Pitching wedge. Thats 7 clubs. Its about how many clubs you can fit in at the top and bottom ends and have 14. Some have 4 wedges, some opt for more hybrids/woods. Adding a 3 or 5 wood to a 4 wood doesn't give you a huge variation really.
Hope that helps.
