Well, I’m not specialized in that area, but my understanding is when the character is human it’s common to use an human generator at least as a basis, and from there you might want to tweak the model to get closer to your reference.
Now what human generator you should use ?
There are a bunch of them, some are free, some are better than others, it’s worth exploring and testing as much as you can…
Beside the model it will give you, you might also look into facial expression , since most of them will provide a rig and correct facial deformation that will come pretty handy once you’ll get to animation. Since even if the model is anatomically correct, bad animation and rig can ruin it.
Here are a few names you can look into :
Makehuman : free, probably a bit obsolete
Manuel Bastioni Lab : free
Human Progress : hyper realistic morphable model, unsure it can handle muscular bodies like your ref…
https://www.reallusion.com/character-creator/
https://www.unrealengine.com/en-US/metahuman
But there are probably even more of them, and since I’m not familiar with these tools , you’ll have to see if you can really use them in blender…