You need to have pollinators, like bees.
The window of pollination is very short (few hours). So if it is rainy and there are no bees, they(females) will be lost. Also, you have to have both male and female flowers.

For decorations, miniture gourds, it does not matter if they matured or not. They will eventually rot if not matureed.
But with the luffah, They have to mature to get dish clothe out of them. I have not yet grown luffah but have seen them sold in Asian market. They could be about a yard long.