I've had a side by side comparison between a native 720p LCD TV and a native 1440p LCD pc monitor, both at 32" diagonal. Tested a couple of games, both 2d and 3d.
For 2d, i've tested Braid, an old 2d game that is 720p fixed resolution. It looked a bit better on the native 720p panel TV. With integer interpolation on the 1440p monitor, the image was sharp but on the same time, the pixels were jagged, most probably an effect of pixels doubling to match 2560x1440 resolution.
For 3d, i've tested Quake Champions, and again, 720p looks worse than on the native 720p screen. Not by much, but there is a difference, it's more jagged...Sharp, not blurry, but no AA settings can alleviate the jaggies. Crucially, 1080p upscaled to 1440p looks way better, especially with some sharpening. I haven't had the chance to test a 4k panel, but i bet 1440p normally upscaled plus sharpening to 4k looks better than 1080p integer scaled to 4k. Kinda like consoles do it.
One thing i've noticed, for 2d games at least, you can achieve similar results with just normal upscaling and tweaked reshade sharpening filters, depending on the native resolution of the panel (ie for 1080p panel you'll have different reshade settings than on a 1440p panel). But it's tricky to get it right...
This makes sense. Integer scaling is way overrated. Mainly useful for pixel art, and most pixel art games, and emulators already have integer scaling options built in.