asking for a some help

Im very sorry if this is wrong place to post this.
if its not the right place where would be good place to be able to ask questions regarding help with making content.

im new to daz studio and im keen to learn how to make content for it.
i do have a little knowledge of using blender and also have started to learn how to use z brush.
i dont know many of the right wording for 3d modelling terms so ill apologise in advance if some stuff isnt correct or make sense. i see parts of models are split on separate and groups and i think i understand that new models need to have separate parts and groups the same or very close to a base body model
what im very confused with is after a making a new model/mesh. (body or clothing) to fit on any of the main base genesis models.
say i make a t shirt and modelled it to follow as close as possible to the base body groups.
as long as its uv mapped do i need to weld vertices back together.
ive tried ti import and anything not welded shows very noticeable seems
i have tried to look up and research on a bit just been having a bit of trouble find info on what im looking up