Apple trees

I've been a keen gardener for more years than I care to remember, through three main gardens. However I have never had any experience of fruit trees, and now I have inherited about half a dozen or so mostly apple trees.

Last year when we moved in they were very overgrown with nettles (up to the tops of the trees!) and brambles. These were all cut back and cleaned up over the winter. Last autumn they all produced some fruit, from a few kilos of cookers - very nice bramleys - to oddments of eaters, a few conference pears on a small falling over tree and a distinct lack of cherries on a cherry tree. And one tree that did nothing at all, appears to be a pear.

This year between the clearing out and the good spring they are laden with fruit, astonishing quantities. Except for the barren pear and the cherry. I know there will be a drop of fruit, and I gather I should help this along. So questions -

When would I expect the drop, and to what extent should I help it along?

One of the eating apples is very badly overgrown with twiggyness and far too many branches, I understand the principles of pruning, but when should I do it?

Thanks for any help.