Originally posted by Lhorn .. I think Godox might have a product but that it won’t work with my flash...
Yup, you cannot incorporate a legacy P-TTL flash into the Godox radio system and still get TTL, but you
can use a Godox speedlight and get P-TTL. If you want on-camera P-TTL as well as off-camera, however, you are limited to the TT350-P ($85) and the V1-P ($260). But if you only want off-camera, the Godox TT685-C ($110) for Canon, or any of the V860II ($180) models, if firmware upgraded to the latest version, can do P-TTL as off-camera radio slaves to a Godox XPro-P, X2T-P or Flashpoint R2 Pro II-P transmitter ($60-$70).
If you don't care about off-camera P-TTL and just need remote group/power control and HSS, the $60 TT600 will work as an off-camera radio slaves as well to the same transmitters. It is a single-pin flash, however, and is manual-only on a camera/trigger hotshoe.
Just saying, while you could get an optical master unit that works with your existing flashes, It's only $180 for a Godox transmitter + TT685-C combo to get off-camera P-TTL/HSS, etc. over radio (so, no line-of-sight requirements) with Godox gear, and you'll have the convenience of built-in radio triggering.
In your terminology-checking:
master and commander are actually the same thing; most on-camera units can be set so they don't contribute light while still giving out the commands from the camera hotshoe. Radio triggers, of course, don't emit any light at all, and the on-camera transmitter unit is also called the master or commander unit.
Slave does not mean TTL control is included, just that it's a remote unit fired off-camera. Slave also doesn't distinguish if it's being used over an optical (light signals) or radio triggering system.
Metz's "servo" mode is more "dumb" optical vs. "smart" optical. Most 3rd-party manufacturers call this S1/S2 modes, though I think Sigma uses Sf and Sd (eyeroll). "Dumb" optical systems use a simple sensor on the flash. Once another flash burst is sensed, the flash fires. S1 fires on the first burst sensed, S2 on the second burst sensed. S2/Sd exists so that if you're using a pop-up flash in TTL, the metering pre-burst can be skipped, and the remote flash will fire during the main burst / exposure. Otherwise, it fires too early. This form of optical slaving, though, is manual only and cannot communicate flash settings: only the fire (sync) signal. But they work across all camera brands.
"Smart" optical slave modes are proprietary. A series of light signals are sent from the on-camera master unit/pop-up flash to communicate settings and information for TTL/HSS, etc. before the metering pre-burst and main burst during exposure occur. As such, they completely mess up the timing required for S1/S2 "dumb" modes, so the two types of systems are incompatible. But the big advantage, of course, is that your camera and flash can communicate to each other for features like remote TTL.
Godox's flashes for Pentax can only do "dumb" S1/S2, not "smart" optical communication. Godox uses radio signalling instead. Radio triggering is often preferred over optical systems, because the light signalling can be overpowered by very bright ambient conditions (i.e., outdoors daylight), and do not require "line of sight" (the remote flash's sensor has to be able to "see" the light signals of the master; so you can't hide the flash behind something solid). And again, used outdoors in bright sunlight, without any bounce surfaces around, the line of sight restrictions can become more stringent with optical systems.