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I'm somewhat of an amateur when it comes to understanding exactly how upscaling and interpolation work, but I have some assumptions that seem visually correct to me.
By 2K resolution, I assume it means 2560x1440 pixels. When you set the resolution in the launcher, you're telling the game to take an image with that resolution, stretch it to the native resolution of your monitor, and fill in all the "gaps" using the desired interpolation algorithm. I hope I'm at least right about that.
The nuance is that if you set a resolution that is not a whole number multiple of your computer's native resolution – for example, if you set 1870x1052 against the native 2560x1440, you'll find that there will be a "gap" every ~1.36 pixels. In general, we will face a rounding problem, and it will look blurry – this is especially noticeable when we disable stretch filters. If you run it in native resolution, everything looks great; if you run it in a "wrong" resolution, everything is blurred. But you can choose a resolution for which your native resolution is a multiple, in other words, so that everything divides evenly. In the case of 2560x1440, you can divide everything by 2 and get the well-known 720p. If you run it, everything will look very good; simply, for every 4 pixels of your monitor, there will be 1 pixel of the game. Accordingly, there is no blur, and this resolution can already be used. You can already apply that stretch filter that your computer can handle without problems :).
In general, with my 2K screen, I play in 1280x720 resolution, and I use either Linear Sharper or Lanczos stretch filters; both look good, but in their own way – this is the best option I've achieved.