It wont matter - either larger lamp or 2 medium lamps. Lumens are lumens. Add em up.
The wattage on LED lamps is BS. How many watts at the wall? Thats all you need to know.
Not "its a 600w equivalent" ... I don't even know what that means.
How large is your grow space, how many plants in that space?
Generally speaking yes the more lighting you have you will get better yields. Up to an upper limit of course. That depends on the size of your grow space and your lighting,