The "as much as necessary but as little as possible" is presumably tied to "tasks" which probably means things that you don't want to do and which generate more pain that pleasure. Because in the field of pursuing pleasures doing things "as little as possible" would not make sense.
This is just what came to my mind as a possible definition of "simplicity". A more detailed version could sound this way: Achieving a reasonable goal with the means it takes to meet this goal sufficiently. On the other hand, not spending resources which would exceed that goal.
Practical example: Buying a well-equipped car for a cheap price from a friend that is still comfortable and fun to drive versus buying an expensive but shiny new car. In the latter case, I would have to increase my working hours or would have to take another job, increasing stress (although a job can also give positive impulses!) and reducing quality time with the family.
Easy to understand, do, or carry out: synonym: easy.
I like this definition!
(This it how family life should be but probably never will be
)