To answers your first question, they say that when you plant in smaller buckets first, the roots tends to grow farther out whereas if you just plant it in a 5 gal bucket, the roots will tend to grow down more than out. Transplanting helps get a more diffuse root system. But, i have never had any problems with just starting it out in the bucket it is going to flower in. It is all a matter of preference. If you don't know how to transplant, then its best to leave them alone because it is easy to kill them.
Yes, strains that you buy are usually going to be better as the pictures reflect. Bagseed is usually pretty good, but you just never know the strain type. The strains that you buy are engineered for highest quality.