pressing 3 smooths the model out, which means it's basicly doing the same thing mesh-smooth would do, except that you cant see the extra polygons added. hi-poly is when a mesh has a high amount of polygons. pretty much 3 gives you a preview of your model hi-poly while the wireframe (in this case) is low-poly. i'd say your model would be a hi-poly if you smoothed it once.

the wireframe is okay in this model, yes. google topology and explore that if you havent already, proper topology is important when rigging so that the quads are deforming realisticly and the way you want. heres a link that shows you what i mean https://phungdinhdung.com/Studies_pap..._modeling.shtm

When a model is finished, then its finished, if you are happy with ur model right now with the amount of polygons and so on then its up to the rigger to deal with it. from what i know the rigger wont smooth your model unless he/she isnt happy witht he amount of polygons. usually before you create a model you would wanna ask the people that are gonna work with your model how many polygons they want it to have.


heres an example of high poly vs low poly : https://www.cgarena.com/freestuff/tut...VS-Hi-poly.jpg