The original Basestars, also know as the Cylon War era Basestar, were widely used in the first Cylon War heavily armored and gunned these ship were the masters of their domain, the ships maneuverability and resources required to build would eventually be its downfall though.
Once the Colonies began mass producing their Battlestars the Basestars would eventually be outnumbered and with the resources they needed to commit to making one would tax heavily on other projects. Keeping their numbers low because of that factor they would rarely commit them into battle for fear of their loss. Traveling in three’s they would conquer their destinations with no remorse, rarely finding one alone Battlestar Commanders would avoid the situation knowing that the other two weren’t too far away.
The complete crew compliment was never determined one ship though had enough personnel to conquer a planet with troops and fighters it was believed their numbers could triple the crew of the Galactica if not more, but intelligence was never received to verify.
Upon the end of the first war, even though the Colonies had more ships they still didn’t have enough firepower and the Cylons not having easy access to more resources could never build their numbers up to conquer leaving a stalemate that would eventually lead to the armistice.
During that time they were able to design smaller more versatile Basestars and making the older models more or less obsolete. Not destroying them or completely scrapping them though they made them more of a platform to haul resources to the Cylon’s home world or the ship called the Colony.
After the destruction of the Colony the newer model Basestars simply vanished leaving the once vast empire without transportation, the models left behind began retrofitting these goliaths and preparing them for war once again.