Hi there so I got this question and bare with me if the answer is so obvious. Just I like to make sure or see if there is something else I should keep in mind for the future. I'm full of questions :) So I finish following this tutorial of this model that turned out well. Now I like to see about bringing it into substance painter to texture it as I like the tools in painter. However I feel it will be tricky. Now in this picture in A, there is my model but as shown in B it has a lot and I mean a lot of triangles. Now I know I should unwrap it but I have to wonder if it normal to unwrap something like that with many tri or not a good idea as it could lead to issue or even might be too much for substance painter. Would I have to say decimate it to have a low and high poly version so it look better for texturing. Just in example C we can see how all the vertices are in that and it quite a mess so makes me wonder how I would unwrap it or would it be something I have to do redo. The same question for D for the body as we see how the body is. Just wondering on that. This isn't for a game engine. I'm just practicing and finish this model and wonder what approach to keep in mind when wanting to texture this even if not for a game just a render. Maybe I might have to decimate or do something else for the unwrapping but thought I ask to see what are good things to think on.
To summarize, asking what step or thought should i keep in mind if i wanted to texture this and not just in substance painter but any other since i like how it turned out. 
Just to let you know, not for a good, just practicing to understand 3d models and texturing better.
For sure unwrapping dense models is a no go. That is why you don't see sculpts getting unwrapped and pushed down the pipeline. You need to have a clean mesh, otherwise is a total nightmare. So unless you're just showcasing the model just because you want to show it or a client has to approve, a mesh with high density should only be used for showcasing, not to push it through the actual production process of unwrapping, UV'ing, texturing, etc. If you're going down that line, it's better to retopo.
Yeah that why I ask the question. And like i said this was just for practice, i was following a tutorial and this is how they approach just making it but i wonder what i could do to texture and least now i know not to go like this if i was to say texture it for a game or so. Also yes it for showcasing, if i may ask, any steps or thoughts to keep in mind when retopo it. This is why I ask these question to understand things better :)
Hi Wolfer! If this will be your first time retopologizing something you've picked a very challenging project! The reasons for this is not only is the model very complex but it is asymmetrical...which means you'll have to do everything "by hand". Retopology is already pretty challenging so you might want to start with something more simple if you are new to it!
As far as CGC videos that cover the subject you might find the first videos in Chapter 2 of the HUMAN course useful. While you may not need to know all the animation/deformation tricks for your particular model the general theories of edge flow, etc are important. Keep in mind though that hard surface retopo is almost its own skillset. I haven't worked through RELIC yet but that course might have some info for hard surface models.
There is also this classic one from Kent, Creature Modeling for Production, especially this chapter, starting here:
https://cgcookie.com/lessons/introduction-to-retopology
wwolfer I understand that completely! I'm the same way. I've got lots of info rattling around in my head but the real challenge ends up being how to put all those bits together in a way that makes sense and gets me the result I want.