We do not have CloudWatch integration for Redshift at the moment, however it's on the roadmap. Meanwhile you could use custom metrics API to push Redshift metrics to Dynatrace cluster. Here are some details:
The DB Service side of things will work. As long as the application that uses Redshift is fully monitored you will see all statements, response times, errors and more.
RedShift is based on postgres and will usually show up as such when used by a monitored application. The jdbc driver is also supported and it will show up as Redshift.