I know that 205 45 17 is the right size tire for my Accord. But I will not be lowering it and I rather not have a big gap. Will the 205 50 17 rub at all?

 

Just get the right size. There is no advantage to a taller tire, and several disadvantages (may rub, throws off the speedometer/odometer, makes acceleration slower, more expensive, etc).

If you want a smaller gap in the wheel wells, the proper way to do it is by lowering the car, not by using tires that are too big.