Imagine that I have 3 different quality versions of the same media on my computer.
HD(1080p) version, 2K and 4K versions. And I have 1080p monitor. Can I see any difference between them on my monitor? (The only difference is resolution. Frame rate and any other properties are exactly same.)
Assuming that the playback software itself has no performance issues, then the only difference between the 1:1 scaled version and the 2K/4K versions is that the latter will have to be downscaled to achieve the same presentation size.
Depending on the downscaling algorithm of the player, you may see aliasing or softening/blurring effects. The video may also look "too sharp".
If the video is downscaled "offline", i.e. before playback, you can choose a variety of filters to downscale the video, which all will look a bit different. Often, Lanczos filtering is recommended for this purpose.
Now, will you see a difference? Nobody can tell you that. Look at the video yourself. It'll greatly depend on the content, the player, the quality of the original encode, and your eyes (or even brain).
Have a look at the following pages for more examples and background info:
