This link discusses some of those questions a little.

Here is a link that might be useful: Selection suggestions for home fruit trees

If you don't plan on spraying them for bugs what is your intention for the bumpy unstorable and mostly unpalatable fruit you will likely produce.

Will 'disease resistant' and 'low spray' types only produce bumpy, unpalatable fruit? Some are immune to the common diseases. We have a few huge, very old (100+ years old) trees here that we never spray that produce big, good tasting, nicely shaped, useable fruit without ever being touched. The skins are dark and look bad, and I wont eat that skin, many locals will eat the skin that way. I would be happy to be able to grow apples like those on smaller trees, the problem with those is the good apples are 30' up, and they are slowly dieing off.

I know some verieties are NG, we have a few huge pear trees here that are full of nice looking fruit that is hard and does not taste good, and I can not eat it. No sweetness at all, tastes wierd.

You should consider grafting your existing trees to new rootstock, as these seem to work well for you.

If you are routinely getting mostly good apples without spray then you are an exceptionally lucky guy.

If it were really that easy none of us would waste the time money and energy spraying our trees.

Around here, the feral (unsprayed) trees will frequently yield some nice apples, some more so than others. But it rarely adds up to much. 90+% of the fruit will be damaged by insects and disease.

If they are not hit too bad, some of those damaged apples can be eaten right away with a bit of carving, and they are great for cider. But you can't store them. and the "passable" ones will still account for under 50% of the yield

If you want a consistent supply of clean fruit then you will almost certainly need to deal with spray or bags or both. DR cultivars might reduce the number and types of treatment you need.

If you plant a whole bunch of trees and then do nothing to treat them, you may also find that your "old reliable" trees stop giving you any good fruit because your pest/disease pressure is going to rise exponentially from all the new "forage" you supply.

Here in southeastern NY I tend old and huge apple trees as a substantial part of my living and unsprayed fruit is not usually very good although Yellow Delicious and Winesap seem capable of producing decent fruit many seasons. Some of the new varieties, like Goldrush and Fuji have given me decent fruit from unsprayed nursery trees when other varieties are pocked with injury.

However, a couple of sprays a season will certainly be worth the investment if you're really interested in producing storable high quality fruit.