If you look at the list of textures / (shader list) then you’ll see if it’s using an image, or a procedural function.
In Photoshop (or any other image editor), you can open that texture map,. and most products have a texturing template ( black and white wire-frame) available on the product page, which you can use as a base (guide) layer, to add /paint your own colours/textures.
Normally, a texture for a clothing item , or figure skin, has a colour (image) texture map, and a grey-scale bump map, which both Fit the item perfectly, using the model’s UV’s, but these are not seamlessly tiling textures. they’re normally made from multiple high-res photographic images compiled into the models UV template. (texturing template) then saved out as a single image texture map.
Procedural shaders use Mathematical functions to apply colours, patterns, fractal noise,.. etc.
so those can be adjusted to increase the scale of the pattern or bump effect.
Your preview window shows the textures in lower resolution and in Open GL, so it’s limited.
you can use the “spot render” or (area render) tool, to render a small portion of your item, instead of rendering the full scene.
Daz Studio has a Photoshop Bridge (plug-in), which allows you to send the model and textures from DS, and edit the textures in photoshop, then send the results back to Daz Studio.
Hope that makes sense and helps