I work for an IBM business partner and this reply is based on my best understanding of the current LotusLive Notes feature set. It's not an official IBM answer.
you choose the LotusLive Notes Hybrid approach, inbound SMTP mail flows via your on-premises servers and you are responsible for scanning for spam.
If you choose the LotusLive Notes Hosted-only approach, inbound SMTP mail flows directly into the LotusLive environment through IBM's AV and anti-spam controls. I don't believe much (any?) of this is accessible to customer administrators.