Yes you use the OEM dipstick with the oil tank....the level works the same way. If you put in the correct amount of oil (stock +1.25qt) and it's overflowing then there are 2 possibilities.
1 You didn't drain all the oil out of the engine first
2 You have a blockage and the oil isn't circulating
Number one is a simple fix, drain out the oil you don't need until the level is correct on the dipstick
Number two, not so simple. And I'd stop riding the quad because it's possible you're destroying the engine. Check that oil flows out of the tank and into the engine by removing the oil feed line from the tank to the oil pump at the oil pump. If you have oil there, follow the chain and check the oil line feeding the top end (you will need to turn the bike over for this, but take the spark plug out). If that's good, move to the oil return line coming into the oil tank. If oil is moving throughout this process then see item 1, where you didn't drain all the oil out or put too much into an empty motor.
It's possible the oil tank manufacturer lied, or that the spec you got with yours was incorrect. If you bought it off ebay, the spec may have been copied and pasted from other atvs that added more capacity than your 700 tank. In all of these cases, you put too much oil into it.