No, not really - only by looking at it in different usage scenarios. Personal preference also comes into play. But I doubt 75Hz would look worse than 60Hz, as 75Hz is a very common refresh rate - and while I'm not familiar with your monitor or how old / new it is, I don't believe using 75Hz would have any negative impact. Personally I would use the 75Hz refresh rate, as I believe it will result in an smoother gaming experience in the games you play that don't drop below 40 FPS or what it might be. You have a 1080 TI after all - when they were realesed I was only dreaming of owning such a high-end graphics card
With regards to the 165Hz of my monitor, it is not the image quality as such, which causes problems, it looks great, also at 165Hz - when you are not gaming.
But my monitor has an IPS panel with a native refresh rate of up to 144Hz and a good response time at that frequency.
Asus has then made an option available - 165Hz - which is actually a factory overclock to the panel's native 144Hz refresh rate. It isn't readily available either, because it is an overclock to the refresh rate, you need to go through a (simple) procedure to activate 165Hz, probably only implemented so Asus has their backs covered regarding technical issues that might arise.
But htis OC alters the response time slightly, for the worse in this instance - that's not always the case, and if you look closely there is some ghosting and a little bit of color bleed.
I know I made it sound as if the image quality is terrible, this is not the case, it looks good, but it actually looks better at 144Hz compared to a slightly lesser quality of the 165Hz factory overclock option, that results in slight ghosting and color bleed.
But my point is still, that I think some are too focused on the 165Hz refresh rate option, that they don't notice some of the side effect this results in. A little bit like variable sync - som people experience stutters, other people complain of mouse input "disturbances" and all sorts of thing. My current setup doesn't even take advantage of G-Sync to a degree that is noticable, because I generally have high FPS output.
I think the 165Hz of this particular monitor is motsly a gimmick. Some e-sports titles on try-hard settings could probably easily output more than 165 FPS at 1440p, but most most AAA titles actualy takes quite a lot of horsepower to output 144 FPS at 1440p with good quality graphics settings, and taking advantage of a 165Hz refresh rate is even harder.
So I'll stick with 144Hz refresh rate and - in my opinion - a better image quality while gaming high paced titles.
But I'm very excited about this monitor, and the combination of a 1440p IPS panel, a decent response time, and a high refresh rate is great, so I don't mean to complain. I still have it's older brother, an Asus 1440p, 144Hz, G-Sync monitor, but with a TN panel instead. I'm also very happy with that monitor, but the IPS panel is just a lot better. Especially now that I use them side by side on a daily basis (and have them porperly calibrated).
But it just shows there are limitations to almost anything in the computer hardware world, and some things sound better on paper, than what they actually can deliver when it comes to functioning outside ideal factory circumstances. There are all kinds of variations in people's PC setups, and in software, and some combinations just aren't tested in the development phase, as it would be impossible to cover everything - sometimes certain features works on the majority of, but not all computers.
And with regards to FreeSync working with Nvidia, it probably works most of the time, but they do mention however, that there are exceptions.