>>49227045>>49227511Going a bit higher isn't that much of an issue. My general rule tends to be to generate at half res first (for example 576x768 for stuff like this or 640x360 for thumbnails for YT or whatever) then when I find a prompt I like I enable hires fix and see how it comes out.
Sometimes if you need significant inpainting it's better to stay at half res until you're done and just manually double it yourself using img2img after. (Since inpainting at high resolution can take a really long time unless your GPU is much better than mine is.) ControlNet can also be useful in those cases to keep it from deviating too much from the current image. (Usually Canny preprocessor works pretty well for this in my experience)
As for what hires fix does I think it's basically just a shortcut to upscale the generated image using img2img immediately after it's generated. I don't know if there's any technical differences between doing it manually and doing it that way though. I think it's almost always desirable for the final image you're going to use since it tends to clean stuff up a lot, pretty much the only time I don't use it is for when I'm going for retro stuff like the PC98 style images since it can mess with the flat shading style.
Also I'm not really an expert on the prompting side of things and other AIchamps probably know more than me since I just kind of learned enough to do what I want at the time but don't have as much time experimenting with it as some people do. 