How to delete consumer groups from non active consumers or Reset the messages lag

Hello,

We ran a trial KSQL container pointing to our cloud data topic, that created a consumer group for ingestion.
After our test, we wish:

1. To understand that these consumer groups (with constantly increasing number of messages lag) do consume disk space.
2. How to delete the consumer group or reset its pending messages (lag) count.

This is in regards to ccloud deployment of Kafka cluster.

Regards,