yeah, you can use SOTA super res, but that tends to be generative too (even diffusion based on its own, or more commonly based on GANs). it can be a challenge to synthesize the right high res details.
but that’s basically the stable diffusion paper (diffusion in latent space plus GAN superres)
Yeah, if you have a high res image, you can get color info at super low-res and then regenerate the colors at high res with another model. (though this isn't an efficient approach at all)