Daz3d is what most devs use, there's also poser (haven't seen it) and on a graphically lower tier you have honey select.
All the ones you mentioned are made with daz, it's free but you have to pay for the assets (expressions, hair styles, etc) but we have a group of good souls that post assets for free on
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Keep in mind that you'll probably need a pretty strong video card in order to make good renders, I saw the 1080ti mentioned as one of the best price/quality cards you can get for daz (the scene has to fit in vram or the card doesn't function at all)