with a GPU in the 1000 Series by Nvidia {or equivalent}.
Misleading, 1000 series means next to nothing. A 1050 or 1060 is worse than a 970Ti. You can get by with much less than that anyway, if single boxing.
Hyperthreading -
Msconfig > Boot (tab) > Default OS should be highlighted > Advanced Options > Check "Number of Processors > Use the cap amount of processors at your disposal > Click "Ok" > Apply > Reboot.
This does not void any sort of warranty, and should be set by default anyway. FFXI is not multi threaded, so multiple threads do not make a single FFXI run any better. If by some miracle you have it off and are multi boxing, it will help.
Setting power option priority for PoL, FFXI, and Windower.
Settings -> System -> Display -> Graphics Settings -> Click "Browse" Icon -> Select program for priority.
Make sure PoL, FFXI, and Windower are stated as high performance.
Irrelevant.
Setting Affinity -
Task Manager > Details > Right Click Pol.exe > Set Affinity > Check only one CPU to use. (Usually not 0 because this is usually used to run all background processes for the GUI)
Irrelevant.
Setting Priority -
Task Manager > Details > Right Click Pol.exe > Set Priority > Select the option you want. (High will be good enough, using Real Time usually causes me issues and causes a crash)
Generally not needed. Windows will handle priorities on it's own, and will generally have better results doing so. Garbage like project mercury doesn't help either.
tldr; There is some useful information here, specifically the low lag dat swaps and how to change FPS caps. There's also a whole lot of snake oil, maybe trim out the bs and keep the good stuff. DGVooodoo or atomos' directx proxy deserve a mention as well.