Yes, reactivity between mouse clicks, is question of speed. I have a Pentium Dual-Core CPU 2GHz and 4Go RAM under Vista 32bits. Is that will be already an archaic machine? Ohoh my PC is an antiquity... Compare to a quad-Core with 16Go, perhaps? "My tailor is poor".

Yes, renderings more "painting" is fun for Art-designers. If you can have an old (antique) Poser, its renderings was really smart for artists, when all the computers was slow, very slow, and the wages big, very big (an other time); and I imagine that is not too possible to take a part of program already made. Also, in Photoshop ou Painter, to destroy a realistic-photo with thousand effects it's a child's play. But may-be the must will be to make a vector render, as if the image was made in Illustrator after 3 days of work by a graphist; I think to the 3D effect in Illustrator, or better, the good & old "Vector-Effects" of MetaCreation (perspective, light, relief & shadow).

Have good MoI.