I am not one for subbing fat with fat free or lower fat.
But, there are exceptions.

Our bodies need  a certain amount of fat to function well.
Our brain needs it.
Our cells need it.

There are fat soluble vitamins that need fat to help them do their job.
The ones that need fat are A,D, E, and K.
CoQ10 and lycopene are also fat soluble.
This is why it is best to have some fat in your salad dressings when you do eat salad.
The fat will help the nutrients absorb into your body better.

One reason that I may substitute a fat with something else is if there is some nutritional benefit.

Fruits and vegetable purees are good because of nutrients and fiber.
The general rule for fruit puree such as pear or apple is to use half the amount of puree that the recipe calls for in fat.
If you are using squash or pumpkin, you will want to use 3/4 of the stated amount of fat.

I have recently tried using avocado and that works. Some people recommend only using half the amount in avocado and half the amount in butter. Others say to use all.
I used all.
The texture was good.
The taste was a little different than with butter.
It also settled after a day and  the difference in the taste was less noticeable.
It idn’t taste like avocado.
Just different than when using butter.
I really think it would complement the taste of anything peanut butter.

No matter what you use, the taste will be slightly different.
Even butter from brand to brand can change the taste a little.

I do find that when making quick breads or muffins that olive oil is a great choice.
It just seems lighter.

Coconut oil, when using the virgin organic that is unrefined and not made using hexane, is a good choice. It compliments the taste of chocolate. It is also high in lauric acid which does a body good.

I also use butter, which is great in it’s own way.