Sierra/High Sierra scaling issues

Hello,

this is my first time posting here after being a Mac user for quite a while. I really never had any kind of problems before but yesterday I ran into one unfortunately.

My Macbook Pro specs:

15" Retina Macbook Pro 2014 Mid

i7 2.5GHz

16GB RAM

Intel Iris Pro 1536MB / NVIDIA GeForce GT 750M 2GB

So yesterday I got my new 27" 4K monitor - Dell U2718Q. I've connected my monitor with the included DP->MiniDP cable to be able to run @ 60Hz. As I connected it to my MBP the default resolution was 3840x2160. As I can zoom in on most of the apps, the UI elements of MacOS is just way too small so I tried various HiDPI resolution modes - 3360x1890, 3200x1800, 3008x1692, 2560x1440. But using all of these modes I get some stuttering, especialy with all the animations like switching full screen apps, opening Launchpad etc. And it becomes quite unusable. Now when I select all of the resolutions mentioned earlier in low resolution mode everything works fine but the sharpness disappears.

What I've also tried is to install public beta of High Sierra, because I've read somewhere on the forums that it should fix this issue because of the new Metal2. But everything is the same. I've also tried reducing transparency, reducing motion, resetting SMC and PRAM but nothing works. I just get these lags whatever I do in HiDPI mode.

So now I am using my new monitor in its native resolution. The text is tiny but it is way more comfortable to use it this way than experience lags. Is there any fix or workaround with this? Is it the MacOS fault or my hardware is just a little bit outdated for HiDPI scaling?

Thank you and sorry for my english.