To err is human. There can be different views and answers to your query but i try to give mine.
Q1 about outline
Outline is better but it depends upon your writing speed. If you have it is advisable to make outline. Besides, as per my seniors, we are supposed to keep same pattern in answering all questions so if your speed is not good avoid outline. You can make it on the rough page in haste just for your help to pick what is relevant to write.
Q2 about keywords
It depends upon nature of question like analyze or evaluate your answer. You have to write answer as per it is asked. Of course there are 20 marks per questions but you have to finish in 35 to 40 minutes so you will have to be relevant else you will miss other questions
Yes it is common in css that word count does not matter but clarity and perfection. If your answer is provided with relevant data, quotations, references, views of some prolific authors, your answer will fetch good marks.
Hopefully, it will help you. All the best.