I think they go hand in hand to a degree. There aren't many "non-processed" (picked off a tree, animal products, etc.) foods which are as calorie dense as processed foods. Having access to something like twinkies or a powerbar makes it way easier to consume lots of calories.

Exactly. Ultra-processed foods are a supernormal stimulus that drives an exaggerated response in humans, e.g. overeating.

The easiest way to understand unprocessed food is "nothing bad added, nothing good taken away".

For instance, pure peanut butter is unprocessed. While it runs through a mechanism to change it from peanuts to peanut butter, there is no oil added, nor are any of the healthful nutrients of peanut butter extracted. Opposite to this is peanut butter like JIF which is processed - the mix is diluted with sugar and vegetable oil to make the same amount of food for cheaper.

Same with tofu - it starts as soybeans and is ran through a mechanism to turn it into the blocks of tofu we see in stores, but we do not add sugar or oils to change the contents of that block, nor do we remove nutrients from the soybean (this may not be 100% accurate, but generally speaking, nutrients are not removed in this). However, many vegan meat products put a lot of unhealthy additions into the mix, thus making it processed.

Generally we put a curdling agent into tofu, so it usually has more of either calcium or magnesium than unprocessed soybeans.

the easiest way to understand processed is has it been changed at all since being harvested? peanut butter and tofu are both processed. raw peanuts and legumes are not. cooked legumes are also technically processed. does not mean that it's always bad per se but that is the definition.

Is low-fat milk processed or unprocessed?

For "processed red meat" people mean red meat that has been preserved by smoking, salting, curing, or by adding preservatives.