The question is whether apples from a diseased cedar rust have any harmful
affects upon humans eating them?

No. Cedar apple rust & other diseases affect the trees. They may reduce the
crop, but won't make it any less edible.

I was wondering also whether it is advisable to cut down and eliminate apple
trees that are badly affected and whether it is good practice for those
remaining apple trees.

In general, it is a good idea not to waste your time on a badly infected tree.
However, the proper way to combat cedar apple rust is to remove any juniper
(cedar) trees in the vicinity.

A practice of finding tree varieties that are resistant to cedar rust.

Of course. But they are not apt to be 100% resistant, so you should still get
rid of the cedars. The usual culprit is Eastern red cedar, Juniperus
virginiana.

So I wonder if a practice of simply eliminating all cedar rust trees and
keep planting varieties resistant to rust is the best practice.

Definitely. But work on getting rid of the cedar trees too.

I cannot change the cedar part of this disease.

Why not? Do they belong to a neighbor who refuses to cooperate? In some states
it is illegal to grow cedars which harbor this disease.

Anyone have actual real experience

I have little experience of growing apple trees in the ground, but when I did I
made sure to get a resistant cultivar. However, around here other diseases,
like apple scab, are more of a problem. I have a bonsai crabapple and a
crabapple in the ground. They are both disease resistant and are doing fine.
Hawthorns are very disease prone. I had a collected hawthorn that came down
with rust, gall, & what not, & I got rid of it. I have an English hawthorn
bonsai which occasionally shows rust symproms, but it is easy to control by
spraying.

Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)