All Metcal STSS and MX systems are ESD safe. I have less knowledge about the other systems so I can't say but I'd be very surprised if not. The tip is grounded. The silicone insulation of the cord between the handle and power supply is also carbon-loaded to prevent static. All STSS and MX power supplies will also refuse to turn on if ground is not present on the AC line, and will power off if ground is lost.
The STSS-001 and STSS-002 are soldering systems, consisting of a power supply, handle, stand, etc. The power supply included with either STSS-001 or STSS-002 systems was one of: RFG-30, PS2, PS2E, or PS2V. The RFG-30 is older and the PS2- is newer. They are essentially functionally identical. I have read that the PS2E-01 has a 30 minute auto-shutoff, but I don't believe that is true. I believe that the timed auto-shutoff was added to the MX-500.
The MX-500 is also generic soldering system name, but it is even more confusing. It may refer to older systems with a power supply having two switchable outputs, or newer systems with a display and two simultaneous outputs. Various suffixes indicate the specific system. e.g. MX-500-S11 includes the MX-500-P11 (120 VAC input voltage, switchable output) supply and MX-RM3E handpiece. The MX-500AV includes the newer MX-500P (universal voltage, simultaneous output) supply and MX-H1-AV handpiece.