With a CZ, at least the metal-framed models, the safety can't be used UNLESS the hammer is cocked, so you've no choice when the hammer is down. (If it can be engaged from the half-cock notch, something is worn or needs attention.).
Carrying with chamber empty is, of course, a matter of personal choice, but doing so assumes that you'll 1) have the time to rack the slide if confronted or attacked without any forewarning, 2) you won't be using your off hand to push someone of value to a safer position, or 3) you won't need to use the off hand to fend off an aggressor (with knife, stick or fists) while you draw your weapon.
For most of us, this discussion will remain a theoretical one, but I would suggest that to plan for the BEST bad case in your training or carry practices is not a good plan. Racking the slide takes time, no intervention from your attacker, and a clear mind on the part of the defender.
Is it safe to have a round chamberred? If the hammer is down, it takes a LONG trigger pull with a CZ, With a decocker-equipped gun, it's still a longer pull, but in either case, until the hammer is fully to the rear, the gun won't fire. If droped, the gun can't fire. If the hammer is slammed, it won't fire. The trigger must be pulled.
Being funny?