This guide is ok but SD Upscaler is outdated.

Watch the video for settings. It is quite complex. If you want to add detail or change the image more try ControlNet+Ultimate SD Upscaler script. It is also easier with the settings: https://stable-diffusion-art.com/controlnet-upscale/#Method_3_ControlNet_tile_upscale

Yes you have to install ControlNet separately.

But you should already see the Tiled VAE and Tiled Diffiusion plugin.

Watch this video to see how it should look. Also a guide for this method: https://youtu.be/KkxNEiiBOyQ

Better than ultimate SD upscaler: https://github.com/pkuliyi2015/multidiffusion-upscaler-for-automatic1111

Combined with controllnet tile upscale it provides amazing results.