In the September newsletter from Propel, they discuss powerful ClickHouse features such as defensive date parsing and introduce new security measures including multi-factor authentication (MFA). They also highlight improvements to their platform, including a serverless ClickHouse interface. Additionally, they provide resources for optimizing ClickHouse performance and feature an article on incremental merges in ClickHouse from the community. Propel offers a free tier with 10GB of storage and 50,000 queries per month.