Also controlnet is so useful.
I also generate 512x512 with 1.6 and then upscale to 1024 with iterative upscaling - adds a ton of detail. Then I can easily upscale to 4K.
If I do iterative upscale to 4K right away it takes like 20h on my m1. But that adds even more details.
And there are negative embeddings which are great eg badhandsv2
So those 4 have been the most impactful for me