First off let me say Welcome!
Now to answer some of your questions:
As to the different geo grafts working together it depends on the set being used. Usually the artists will find a genital they prefer (I'm usually more going for a Golden Palace and Headlights combo, though I will occasionally use New Gens, and rarely use the Daz Anatomical elements.) There is one thing to look out for and that is a lot of the geo grafts use geoshells to add more detail or effects to the genitals and if you apply multiple geoshells they can clash though it is not a hard thing to fix and some vendors even include shell fix scripts to fix the clashing.
Textures are pretty easy to use on a lot of the various geograft genitals, as most are mapped to use the torso map and shaders on the genital object and include scripts to copy the materials from the base figure to the gens (In most cases you have the Genesis based figure selected and run the material copy script and it will copy the torso setting to the genitals) and then an additional geoshell to add more detail (an example being the Golden Palace geoshell applies different shader settings to the labia and anus, and New Gens has two shells one adds coloration to labia and anus, the other adds effects like displacement (swelling of the labia majora) and wetness settings)
For poses that use a preference in genital models, most of them the genitals poses are separate poses that is applied to just the genital (You have the main pose for the Genesis figure, and the select the genital model and apply the gens pose) So most of the poses if you have a different genital model, you would just use the base pose, and then manually pose the genitals.
As to morph sets for the Daz Anatomical elements they exist, examples being Powerage's G8M Genitalia Toolbox, and Eroticalist Veiny Wet Cock and Juicy Wet Cameltoe, Poison also has products that add morphs to the anatomical elements . Though even with geografts Daz does not spend a lot of time adding detail and bones to their grafts so you end up with very basic genitals with limited uses, whereas with Meipe's Golden Palace for example, you have rigging in the labia as well as lots of morphs to adjust the look and shape of the Vulva as well as how open or gaped you want the vagina or anus.