How to bend handlebar to customize it?
No! Don't do it!

Certainly not with aluminium / alloy bars. Any bending stresses the internal structure of the metal, weakening it. Even in a metalworking shop, I would be doubtful of the safety of the product. I hesitated to say final product because the result could be ... final. For you.

Even with steel bars, I wouldn't do it. With steel bars we used to bend them slightly to have our preferred shape. But the wall thickness of steel bars these days is so low that I would not recommend even slight bending. With such low wall thickness almost no amount annealing or other treatment will restore full strength.

The other thing you mention is using plain pipe. Since it's not high-tensile steel (it'll be plain carbon steel), to be strong enough it will have thick walls and be heavy.