Step -1. You should have already done this
1. Get FFXIV's stupid ass spatial audio thing. It has a trial. Do not buy this thing. It's implementation is why you are having issues to begin with. Download it at
https://embody.co/pages/ffxiv . Make a picture of your ear for esoteric audiophile pseudoscience reasons. Enable spatial audio in the FFXIV Sound Options. Be infuriated at the irony of having to install the very thing that broke audio for you, to remedy the audio by a little.
2.) Set your listening position all the way to character
3.) Set ambient Volume as low as possible (1,2). DO NOT mute Ambient and do not set it to 0. Also make sure wireless controller Speaker Sound is set to none, Volume 0 AND muted. Equalizer: Standard.
4.) System Configuration -> Other Option -> Character and Object Quantity: Low
5.) Character Configuration -> Control Settings -> Character -> Disable or Show Limited on Party and Others.
6.) Windows Control Panel -> Sound -> Rightclick your Device -> Properties -> Enhancements -> Disable all Enhancements
7.) Advanced Tab -> Default Format as low as possible
8.) Spatial Sound Tab -> Off
9.) Blatantly ignore square's condescending, illinformed, maliciously reductionst advice to use DX9 out of sheer spite. If their reasoning for our issues is "your CPU is 10 years old" - our reasoning for not using DX9 is "It's 27 years old". Fuck that.
10.) Apply "official" fixes anyway and scale down graphical options as per the official reply in this thread. Enable LODs and such.
11.) Make sure neither your GPU nor CPU are overheating, or running at near capacity when playing FFXIV. Lower settings and/or improve ventilation if that's the case. If you have low FPS in addition to audio issues - you already failed here and are skirting the line of minimum requirements. Your CPU might get a little hotter and be a little more taxed because of the audio issues - sending you over the edge, where your CPU desperately down throttles to not katamari itself. Run the benchmark test further down - if that is you.