I think a workflow I use can be helpfull for you too.
I use 3d scanners instead of photogrammetry, but it can be applicable for photogrammetry and blender.
I cannot show my projects due to NDI but what I get from 3d scanner is something like this: https://www.artec3d.com/3d-models/borderlands-cosplayer
This will be the "High-poly mesh".
Then I optimize the scan in Artec Studio to reduse the number of polygons - the result mesh is still messy, but can be processed in software like Blender of 3ds max without putting my PC on fire. However It's still too messy to make a good UV map, so next step is retopology. There are two ways - change existing topology manually or create the new topology above the old one, like in all retopology tutorials. However, I'm too lazy, so I prefer the 1st way if possible. Then I unwrap the result mesh. This is "low-poly mesh" - It doesn't have to vave as less polygons as possible (Actually this depends on what are you going to do with a final model) - but simple enough to make a proper UVs and comfort workflow.
Then I bake the color map (that one with messy UVs) and normal map from high poly to low poly. To get more detailed normal map I use as high poly mesh as possible.
I use Substance Painter for baking, but you can use blender, if it works good with high poly.