Thanks for posting! It looks like you have a spiral balance for a non-tilt window. Is that correct? If so, can you also give me the diameter of the spiral? It looks very skinny, so just by eye-balling it I think it could be 3/8", but I would like you to confirm just to make sure.
Also, when measuring the length, are you measuring the tube only? Please confirm that only the tube is 30" long.
Yes, the tube is 30" long and the spiral is 3/8"
Will using the sash with the higher weight capacity inhibit the functionality of the window at all? I.e. will it be harder to open or close?
If your sash weight is below the threshold for the Green Tip, then yes, the sash will be harder to open and close. However as long as it's within the range of 14 though 26 pounds the window should operate fine.