This Option doesnt exist for the wiim amp pro
Correct. And actually this setting should not be needed at all to get LipSync over HDMI ARC.
The Synch Audio setting is intended for devices where WiiM doesn't have full control over the entire system from the input ports to the speaker outputs, which basically means all the streamers, not the amplifiers. In this case people are adding their own amps and potentially DACs, maybe even other devices. All these devices can add an additional delay to the processing and Synch Audio is intended to take care of that.
I remember somebody (maybe
@hgo58?) mentioned that using Synch Audio appeared to cure lip synch problems in their setup. It's not totally clear if this really was the cure or mainly coincidence. Others have mentioned that their issues went away magically without using this option.
Using at the LG OLED TV audio bypass and at the wiim app 150ms
This 150 ms setting on the Group Audio Delay page
should apply only if you have linked two or more WiiM devices in a group. It shouldn't make a difference otherwise.
You can still try if lowering this setting to 70 ms or even increasing it to 800 ms for testing purposes does make a difference, but it really shouldn't for one single WiiM Amp Pro.
HDMI ARC does support a "dynamic" automatic lip synch correction (but I have no idea how it works). For one, this requires an HDMI 2.0 or higher compliant cable, while HDMI ARC is supported from HDMI 1.4 on. Using a
new and certified HDMI cable (2.0 or newer)
could help here.
Finally, you should have a close look at your TVs sound settings. When you say, it is set to audio bypass, does that mean you are actually feeding the TV from another HDMI source and you don't have any sound settings available in that mode? In this case, the source device might provide such settings.
Good luck!