Will try to get into as many details as possible, but simply increasing a texture map resolution does not necessarily increase quality as well and will try to demonstrate it the best I can. Also I think it might be a common misconception that people might have when making textures, which is understandable as its very reasonable and correct that the more pixels you have in a texture map the more details it can also contain. But whether the quality of the texture map is therefore also improved is not correct, because it completely rely on the source material used.

Render settings in Firefly or Superfly doesn't really have a lot to do with quality in regards to textures, but more whether the final render of the image is of high quality, so regardless of render settings, if the textures used are of low quality or wrong resolution, the final render will also be of low quality. Even though all the render settings are very high.

Here is a plate of food which I will use as example. The object is split into 2 parts so there is a plate texture and a texture for the food. The plate texture I will leave unchanged and only change the food texture. The original texture size of the food is 1024 x 1024, which is fairly small in general for Poser textures, usually I think most people will use 2048 x 2048 or even higher, and again in some cases I think it might be due to the misconception mentioned above.

Number 1 to 3 is the quality of the object as it is in my product, but just rendered using different pixel samples. As you can see when looking at the actually food texture there is no difference in quality, the final render with 10 pixel samples is obviously worse, because it uses lower render settings than the one with 40 so it contain more noise etc.

Number 4 and 5 are using textures size of 128 x 128 and 256 x 256 and its pretty clear that quality or details are starting to get lost, especially in the 128 x 128 it starts to become blurred, which is due to the texture map simply not having enough pixels to correctly maintain all the details that were in the source material that I used, so it will try to push all the details into those pixels, which will reduce quality.

Number 6 is pretty much the opposite because it suddenly have a huge amount of pixels available and therefore it will try to stretch the information from the source material to fill all this extra information. Now it doesn't look as bad as with lowering the quality and you can easily get away with it. The problem here is mostly due to the size of the textures compared to the "assumed" quality increase you get.

Because comparing number 3 and 6, its almost impossible to see any difference. However comparing the size of the textures. Which in this case is using 2 maps a diffuse map and a normal map. The 4096 x 4096 clock in at a total of 3.42 MB for the two maps, where as the 1024 x 1024 is only 365 KB.

Also cranking up the resolution to 4096 x 4096 makes little sense as the source material from which i cut out the food texture is only 1500 x 1500, and cutting away all the stuff I didn't need, I can see that a rough estimation of the actual source material is around 1180 x 1180. So scaling it down to 1024 x 1024 makes a whole lot more sense in terms of quality, than to crank it up to 4096 x 4096 which in the end will not really do me any good.

Last thing is the size of the object in comparison to everything else. Since this is a plate of food, it is not really big compared to lets say a Character or a Wall, so using smaller texture sizes for stuff like that makes sense, compared to a Wall, which might be huge and would suffer very badly in quality, if you used a 128 x 128 texture on it.

I hope it makes sense and that you can render your stuff with fairly low render settings, if you just want to test the quality of your textures. The only place where render settings are important is to reduce noise, make sure that lighting is correct, like bounces etc. Transparency, if you render water or glass and want correct quality that you use caustics.