Yes and no. For starters, it's all about assets (it's no secret Daz is in it for the money). At the basic of basic, yes, all you can do is download characters, mix and match features, and tweak a little bit. I'd say that's what most people, especially new creators, do and part of the reason it seems like you always see the same characters in every game. However, there are quite a few morphing assets that you can get that allow for a broad range of modification.
For example:
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The cost and need of all the assets is one of my biggest gripes with Daz, and one of the main reasons I still use G3 characters instead of G8, I have a lot more assets for G3. However, as far as clothing control and everything else, that is typically asset specific (depends on how much work the designer wanted to put into it) and a lot of assets have quite a bit of morphing freedom(example below). Also, you're not limited to Daz's website for assets, many independent artists sell (and sometimes give away) assets on sites such as renderocity.
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I'm not trying to convince you to use Daz or anything. Use what you're comfortable with and enjoy. You're obviously capable of doing a good job with HS, I'm just explaining why I personally made the switch to Daz.