Question 1: If you do a gorgeous transition through walk, you will get an excellent score. If you do a gorgeous transition without walk, you will get an excellent score. For almost all training level horses, you are more likely to nail it t through the walk, so you should do that. There aren’t really any bonus points for doing more than requested, but they will not hesitate to give you a low score if you try for the harder transition and do it poorly.
Question 2: The judge won’t care. Unless a specific movement says you must post (the stretchy circle used to?), you can do as you please. That said, most riders at training level will score better if they post because they are more likely to ride the horse freely forward, as required in the directives of the level. That translates to an increased gaits score, and a bump in every trot movement.