I cannot believe that old fallacy is still circulating around.
During the Greater NYC toilet change out, a lot of folks were saying the new 1.6 GPF toilets would cause major problems compared to the old 3.5 GPF.
They rambled about no scouring action able to take place AND how the horizontal piping would constantly be a source of stoppages. NEVER HAPPENED
NYC replaced around 4 MILLION TOILETS saving billions of cubic feet of water per year.
Now in your case the low flow flapper most lightly will NOT WORK. You see it is how the toilet is designed not just one component. Like the folks on the LEFT COAST (California) putting bricks in the toilets to help conserve water during the draught BUT then they had to flush twice.
If you really want to lower the water waste try getting a GREAT Crane toilet 1.6 They cost around $59.00 and after installing several hundred of them NOT ONE CALL BACK.
I wish I could say this about the other TWICE as expensive types. The Crane is Quiet and has gravity flow and most of all it WORKS, but the reason some folks don’t push this toilet is they cant charge a lot for this fantastic product.