i just want to note some useful stuff i figured on the way:

if you have a relevabt item that you want to be more meaningful in the evolution of a pet, use it at an early stage where you can feed it just few items, then fill the rest of the feeding requirements with some heat or resource, something that will not dilute the significance of the important item. Think of this like this, you ask an artist to drau 70 items on a character, or you ask it to draw one plus a lot of filler..when will the one item look better and more relevant..its obvious.

be careful, crits do die..and if you do the above you can significantly lower its bars and risk killing it, so keep an eye on that don't overdue. best if you can find a combination that does not make a salad.

feeding affects the bars, and bars affect the way it looks, but its complex, evwn hard to describe, so the exact effects is yours to observe, i just gave you a clue on what is changing what.

oh and if you want a cute pet, do not feed it creatures ..as in never.. flesh eating pets are never cute and ..whats the word..you know..

Are there any bonuses for feeding it extra of something? Did you ever figure out how tokens influence them?

i dont know to answer you that.. if you find out let me know.

The image model sometimes interprets things literaly, some times depending on context it ignores them..it all depends on how those tokens fit with the rest of your context and offerings.