[...] come on, would you care to tell me more - where to look for the first 3?
You didn't asked where to get those
tell us more about your specifications and you might get fruitful answers, directions and maybe, even maybe links
Not sure 100% [...] but
A. lo mem = textures swapping more often
B. VRAM is slower even than system memory, albeit video mem.
C. I guess rendering time increases with texture size.
If you want to have a multitexturing shader, you have to sample for each pixel N colors for N mixed textures plus one or more texture samples for the blendmap, plus one sample for a lightmap, if you use one. If you use normalmaps, things might get complicated and you need two samples for each texture (1 texture and 1 normalmap fetch).
If you want one single texture fetch for color + normal, you could use a two-channel colorspace encoding scheme like RG color space (Technicolor, see
Wikipedia) and only X and Y component of the normal, while you decode the color and the missing Z-component of the normal in the fragment shader.
Other than texture samples, one drawback is also the amount of data you push through your GPU card. The bigger the textures, the more data is going back and forth, and, yeah, that could reduce performance as well.
BUT, this depends only on your specifications.
Tell us.
