RG-6 cable can span longer distance than RG-59, but I'd guess we'd be talking orders of magnitude longer than 2m before the losses become significant.

At 2m or less, I don't expect you'd see much difference.

If you had an external device like another LD or professional video monitor providing a sync signal, then I think you'd turn that switch on.

Without an external sync connected I believe you should leave that switch off so the player generates its own sync pulses from its internal clock.