The bus terminal is near the ferry terminal, just walk along the covered walkway. Note most of bus services from the terminal are long distance to Kuala Lumpur and may be expensive if possible for a short ride to Aloe Setar or Butterworth.
There are electric train serving Arau, from Penang and Kuala Lumpur. From Arau you can complete the 20KM journey to Kuala Perlis either through bus or taxi.
Apart from Penang and Kuala Kedah, Kuala Perlis is another ferry point to Langkawi. Langkawi Ferry Service  provides ferry service to Langkawi island.
Nightlife is non-existent. Beers can be purchased at all 7-11 convenient stores.
Avoiding overly revealing clothes goes a long way towards blending in. Many mosques and temples require covering up, and you will get more respect from officialdom if you dress up a little. Many places of worship including all mosques will require you to take your shoes off before entering. When eating with hands rather than cutlery, do not eat with the left hand in public as it is considered impolite. If you can speak just a few words of the four main local languages, namely Bahasa Malaysia, Chinese (especially Cantonese), Tamil and English, it will ingratiate you a lot with the locals.
Average temperatures are hot or hotter; it's the tropics. Be sure to stay hydrated. You will need to drink about 3 litres a day and don't wait till you are thirsty to drink. Room temprature water preferably. De-hydration accounts for a large percentage of dodgy tummy holiday illnesses.
Perlis is relatively a safe place for travellers, however like in any other place, Perlis has its share of crime, so common precautions must be taken against snatch-thieves and scams. Some other precautions: