G-sync is a specific Nvidia tech. It only works with Nvidia GPU. And monitor manufacture has to pay for using its tech in its hardware through licensing which is why g-sync monitors are expensive.
Freesync is an AMD tech but it is an open standard meaning manufacturer can put that tech in monitor without paying a license fee. Freesync is like an industry standard for variable refresh rate monitor much like OpenGL standard for graphics.
So regardless of what brand GPU you have as long as it supports variable refresh rate, it will work with Freesync give the monitor is Freesync capable.
v-sync is different to free sync. V-sync is really old way of trying to sort out screen tear and artifacting during gaming. If you have Freesync switched on you do not need to have v-sync on as the two tech is not compatible as far as I am aware.
regarding those settings, standard ultimate. they are the strength of variable refresh rate adaptation. Each monitor has different setting and capability. You need to search the net for some reviews on wha the best setting it is for your use case. For instance my AOC G2U has 3 settings - low, medium and strong. My games FPS are over 90, so the timing between each frame is small therefore I need to have the setting at strong as that gives the quickest response. But if I have games only doing 60fps then if I have the setting at strong, the monitor will over shoot the response - causing ghosting. Therefore I need to dial that setting back a bit to medium.
hope the above helps.
lastly to take full advantage of Freesync or Gsync in normal windows application, you should go into video card setting and cap the refresh rate at 1 frame below the maximum Hz of the monitor. So in your case cap it at 143FPS. This ensures the variable refresh rate engine is working all the time to give you that butter smooth graphics. You will notice the difference - by just moving the mouse across the screen.