Wheel Alignment

So we all can look up what the 'correct'settings and tolerances are for wheel alignment (castor, camber, toe, etc.)

But what is the (thirty years now) perceived wisdom of this?

What differences does it make to the handling taking the wheels towards one end or the other of the tolerances.  Or indeed over them?

Presumably there's things we can do to get a sharper turn in, but then we'll get a more tail happy car, which is to some tastes but not to others.

And is it still true (like the book says) that the rears are completely non adjustable?

Going in to have the (awful) struts and ARB's the car came with removed on Friday, and a lovely set from a previous Golf of mine (set up by Ray West at Thruxton) put on.

Car as bought is simply the worst handling car I've ever driven (Allegros, Marinas included)…will go from power understeer to lift off over steer wuicker than a 70's 911!! , while previous one was simply the best front driver I've ever known…  Hoping to get the old magic back.

So answers quick,. pls, from the wise old guys on here.

Cheers from Al