Hi Antara!
I make only animation and I don't accept any compromise on the quality of the renders (everything is checked in the up render tab).
If one needs 48h for a sequence of 6 seconds, it is not a problem, you stop it when you want and you start again when you want with the following image (you can sleep when your PC is working).
I rarely use the global illumination but my scenes contain a quantity of lights intended to emerge the "black holes" and, only one, the principal one, catch the shadows, the others are allotted to separate objects (except interior scenes with a few electric lamps).
I often use compositing for special effects (AE/Combustion) and it is for that I makes almost all the time Targa sequences, but for the “normal” scenes, I make .bmp sequences (always use square pixels).
About speed, I strongly disadvise you not using the number of fps equal to the final project because you will lose enormously in quality.

edit: you can import .bvh, .pz2 directly in your character in Carrara.