Macs use airplay 1 for audio only streams.
airplay 1 has a couple second delay due to buffering, it always has, and not a mystery.
depending on what you're using to play video, apple used to do some trickery, and delay the video on your Mac so it matched the delayed audio coming out of the speakers, it's been a while since I've dealt with this, so don't remember the details, or know if it still does this.
the wireless audio sync won't help, that's to get audio being streamed from an appleTV to a wireless speaker in sync with the video playing on an appleTV. Since the audio is delayed before the appleTV plays it, it will still be delayed even if the aTV is playing the audio in sync with it's video.
doesn't matter what aTV (2, 3, HD (previously know as the 4) , 4K), or if you have HomePods connected to it, or the software version, or what device you're streaming to (appleTV, homepod, airport express, or speakers from a number of different manufacturers), since it's airplay1, it will always have the delay.
If you enable screen mirroring on the Mac, it will use airplay2 to send the audio alongside the video, and the audio will not be delayed. You can choose either mirror or separate display, both ways will work.
for a slightly better experience sending audio from the Mac, there is an app called airfoil by rogue amoeba, it allows you to pick a single app to stream audio from, so you can choose whatever app you're using to play audio. and you won't get mail alerts, or the audio from random auto play videos on webpages coming out of your speakers. I used to use this all the time, but it's been a few years, it might support airplay2 now, but not sure.
