We were in the diet and health food manufacturing business. We formulated with sweeteners for years. The sweetener I use to replace sugar (1 to 1) is an all natural Monk Fruit/Erythritol blend like Lakanto.
Most sweeteners that advertise using Monk Fruit are bulked with something as the sweetener itself is about 300 times more sweet than sugar.
Erythritol which is an all natural sugar alcohol is a near perfect bulking agent.
Lakanto makes a baking blend of this formula also, as Erythritol can "re-crystalize" after heating. It is low glycemic, so won't raise blood sugar levels.