TL;DR dump your Yongnuo gear. Get Godox. But you may have to give up remote zoom control (tradeoff: you'll get HSS and a lot more elbow room for expansion).
Marm O. Set wrote in post #18661494
... I have a 685 on the way but haven't ever messed with them before. My understanding is that the 685 will not master; is this correct?
Yes. It's only a 622 radio slave and does not have master capability in it.
...So I can't have the 685 on TTL AND use it to fire the 560s?
No, you can't. And the only way to get the 622 system to fire 560s is to use 603 mode, which then makes the 685 act like a 560, so no TTL. You might be able to put a 622 on the hotshoe, stack a YN-685 on the passthrough hotshoe and still fire the 560s, but if you don't want to sandwich a trigger, then the Godox system would be a much nicer, far more expandable setup and in the Godox X system, you can use the on-camera TTL speedlight to trigger off-camera manual-only $65 speedlights.
Godox's system is missing a few features the Yongnuo system has: remote zoom control is far more limited (doesn't work with manual-only flashes only the TTL ones, and only if Zoom on the flash is set to Auto and you're using an XPro transmitter), and there's no remote wake-up. And you can't use one unit as both a shutter release receiver and a flash transmitter. But. Unlike using YN-560-TX and YN-560 III/IV, you will have HSS over radio. The Godox TT600 is a single-pin manual-only flash with a built-in radio transceiver. Like a YN-560 III/IV, it can be remote power controlled and fired from a Godox transmitter unit. The Godox TT685 is a TTL/HSS capable speedlight with a built-in radio transceiver that can be used as a TTL/HSS radio master on the hotshoe to the TT600s. The TT600 also has a Li-on version, the V850II; and the TT685 has one, the V860II. These li-on versions are identical to their AA-powered counterparts, except for not having an external battery pack port, since the rechargeable li-on battery pack they use basically takes the place of an external pack, lasting roughly 2.5x as long as 4xAAs. This can greatly simplify battery handling if you're an all-day event shooter.
The TT600 is $65; the V850II is $140. The TT685 is $110; the V860II is $180. And getting them from Adorama or B&H will give you a full 1 year warranty, covered by Adorama or B&H, which means for support you're communicating with someone in NYC, not getting your emails to Shenzhen ignored.
In addition to having TTL/manual-only gear that works together, the Godox system also includes larger bare bulb flashes and studio strobes. And, when used as off-camera radio slaves, the lights in the system can system switch to any of the five supported camera flash systems: Canon, Nikon, Sony, Fuji, and MFT. So, if you need to share lights with a different-system shooter or you add mirrorless gear to your SLR gear, you don't need to rebuy lights; just the on-camera transmitter unit. For example, I have a TT685C which I can use in TTL/HSS on-camera with my 5DMkII, and off-camera with my Canon 5DMkII and Godox Xpro-C transmitter as a TTL/HSS/power controlled radio slave. And as a TTL/HSS/power controlled slave to my Fuji X100T and Godox XPro-F transmitter. And as a TTL/HSS/power controlled slave to my Panasonic GX-7 and Godox XPro-O transmitter.
The XPro transmitter has a few more functions than a TT685/V860II as a radio master, such as TCM (TTL convert to Manual; a kind of way to lock in the power TTL sets by converting it to an M power ratio setting).