I only heat up a little bit of juice with the sugar in there. I try to avoid using any extra stuff like K meta. I don't even like adding pectic enzyme to my wine
That's your choice, of course, but pectic enzyme is as innoculous as can be.
Just to split hairs, making cider isn't "brewing". When people see the word "brewing" in a title, they immediately think that you are brewing (beer). Cidermaking is very much like winemaking, and generally winemakers and cidermakers don't heat their musts because of a cooked flavor in the result.
Think of a crisp apple from the tree. Then think of an apple from an apple pie. There is a distinct difference in the flavor, and not just the texture. The crisp apple has a tartness and "bite" to it that a cooked apple (even without sugar) does not. That's the basic difference between cooked fruit and fruit juice vs not cooking.
When I've made cider and my grandson was very little, I did pasteurize the juice very briefly because his mom was worried about ecoli. To do that, just like with pasteurizing milk, go to the lowest possible temperature that is effective. For milk, it's 160 degrees for 30 seconds (and then immediately plunged into an ice bath to cool) or 140 for 30 minutes.
I no longer do this, as my daughter relaxed after her next kid came along, and we don't pasteurize our drinking cider for the little ones but we are very careful not to use contaminated apples (we have a lot of deer, and under the apple trees there is a lot of deer poop!) and wash them as well.