Disclaimer: I'm not in tech support, this is just my layman's troubleshooting routine
Short of checking different possible causes you can't really tell.
In my case the game was crashing on loading screens or immediately on startup throwing various DirectX errors.
Looking at the system this would happen when RAM was getting rather full so I tried what happens when it was mostly empty and the game was fine, further testing revealed other programs running into issues intermittently (browser tabs crashing, Discord going unresponsive) whenever the system was using more than half the available RAM so I threw Memtest86 at it and did get a crash eventually. Trying individual RAM modules I found out one of them was faulty and whenever something tried to access the broken sector I'd get issues.
I've RMA'd the module with Corsair and am waiting to get a replacement from them.
You said you had artifacting and graphical glitches, though, and those usually are a good indicator for something going on with the GPU so I'd be leaning towards that.
This is why I suggested stresstesting the card to see what happens.
If it consistently runs into issues under stress you can try stuff like debug mode in the Nvidia control panel to enforce stock clockspeed and see if that fixes it, if it does your card is (factory) overclocked and doesn't like it for some reason or another so underclocking could be the solution. If that isn't fixing it you'd at least know that the issue is likely with the card and could go look for a solution from there.
If it handles the stresstest just fine you can try specifically testing with a DirectX test, since I think my go-to FurMark is OpenGL/Vulkan only, just to see if the issue is specific to that API.
If stressing the card doesn't indicate any issues with it but you can replicate issues in programs other than FFXIV it might be some other piece of hardware, in that case I'd just keep an eye on the resource monitor when it happens and maybe see if there's anything in the event viewer that can point you in the right direction.
If the card handles stress without issue and you can't replicate the issue outside of FFXIV that could indicate a software issue rather than a hardware one.
And lest I forget the simplest troubleshooting step of them all short of turning it off and on again: simply reseat the card to make sure it's in the slot correctly.