New user, new to 3D 2 weeks ago - first model help

Ok so i saw this new thing"sculptris" “oh wow” free and easy to use “im in”

I got straight into in it last week and loved using it but ive no idea if im doing anything right. Ive created my recently lost pet “zigg” the cat. The head / eyes/ whiskers and ears are all separate models.

My first question is for adding textures, should i ever get that far or painting, is it best to have the mesh as “one” or in separate parts?

Second question is with the eyes. Ive seen in other models that the eyes have great hollows in them. Should i bore out behins the eyes before adding spheres? If so why?

These questions might not be simple to answer. I git so carried away with trying to get the best possible likeness, he was a dear friend, i didnt even consider if i was working to best practices. I just wanted to see him in 3D!

Can anyone offer some tips?