All metal or coin mode??

I would probably set it to reject pulltabs, then go from there, would lose nickels and smaller gold rings, but silver would be fine. On the other hand if its a very old site, I would just dig everything. Could be some nice relics there

You mention coin 'range'. If you can fine tune the discrimination then set it so small iron is heard but gives a breaking signal. Then you won't lose much depth yet can still detect without going mad.
If you think it might be a good site then all metal may be the way to go and you should be able to ignore much of the rubbish by either sweeping the target both ways to check if one direction gives the double blip of long bits of iron such as nails and by finding out the maximum depth your machine will go to on the site and checking how far you can lift the coil before the signal disappears. If you can detect a large coin at eight inches 'in ground' but the signal hasn't disappeared when the coils lifted 10 inches then its not likely to be a coin.
Other thing to try is to ignore the loud near surface signals and only dig the weak deep ones.

Listen to Brian here. He makes a lot of sense. Also , it is true that when the discriminator is engaged you will lose some depth and it will get worse the higher you turn it up. Motion VLF detectors developed by George Paine for the Bounty Hunter Red Baron were the revolution in the industry where you could keep most of your depth and still disc out trash. Many detectors today are some sort of version of that technology.

ok will give it a shot. As a general rule , does the all metal mode detect substantially deeper than having my settings on coin range? Also , if I set it to all metal mode and get a bleep in one direction only , can that also be a possibility that it is in fact a coin but too deep to have a bleep sweeping in both directions? { or even standing on edge?}

That can depend on the same factors as with disc on. Ground mineralization , etc. all play a part in how well you detect an object. All metal will generally go deeper. Usually a solid signal one way and no signal or a cutoff blip the other way could indicate a coin on an angle or on edge.

All metal WAS always the deepest mode to use though with some machines on certain mineralisation a fraction of discrimination could act to balance out the minerals and you could gain a little depth.
With later motion machines a low level of discrimination may well be deeper than all metal. You just have to see what works with your specific machine.