I'm not an expert but I do use Daz Studio.  It's been my experience that the more you put in your scene the slower the program will GET while you are working on it.  I don't have any problems when I first load a scene...but if its a big scene, the longer I'm working in it the longer it takes to do some things.  Daz has a bad habit of grabbing your resources and not wanting to let go.   :rolleyes:

There are lots of people here that know more than I do and maybe some of them will jump in and advise you also.
As for the clothes. I find it easier to clothe the model before I pose it.  If you learn how to 'tweak' the clothes..you can make the same outfits fit different characters...like David to Michael...and there are programs out there that people use to make one character's clothes fit another...but I forget the name.  I just do the tweaking  ...
V3 clothes should fit V4 without much problem.

Good luck and welcome to the community here. 

 

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