Depending on the source and your PC Specs. It may take a hour, it may take more than a hour or it may take less than a hour. If your encoding SD (3600 , 480p or 576p) It takes less than a hour if your PC Specs are ok.
That depends on what you want. A Mini-mkv 720p should be around (100-130MB) Here I allowed up too 150MB if the Series is a high Action Graphics example a mecha needs a lot of Size because it has a lot of action Graphics material.
No, unless your referring to make a batch. On cyko yeah you can make a batch to encode everything on the same settings and not put one after another.