Should I sterilize these bottles?

Yes. Sterilize all new bottles, rings and nipples at least 5 minutes, you can not assume they are sterile or clean when you purchase them. Also, depending where you live it might be necessary, if you drink well water for instance.
Why ever? This is a practice that dates back to a time when moms made formula from evaporated milk and had to boil the milk to make it digestible.City water supplies were also inconsistent. Today it is a waste of time unless you are unsure of your water.A good bottle brush, and hot soapy water will work well for both.