2 Answers
Yes, you can use either. Secrets Manager is newer, it comes with features such as automatic key rotation, random secrets, etc.
https://acloudguru.com/blog/engineering/an-inside-look-at-aws-secrets-manager-vs-parameter-store
A couple of other differences. Parameter Store incurs no cost up to 10k parameters where Secrets Manager costs $0.40 per secret. An advantage of Secrets Manager is that you can allow cross account access to secrets.