You have 4 different ways to impact what data is shown in Velocity:
Data scopes allow you to limit the data your team has access to
File exclude roles allow you to exclude files from code analysis. This can be handy if you'd like certain files or directories to not contribute to metrics.
Branch excludes patterns allow you to specify which branches you'd like to be excluded from risk assessment. Any pull request whose branch matches one of these patterns will not be included in the reports
Types of metrics we get in Velocity
Velocity metrics - calculations we do to existing Git/JIRA data
Git activity - pulled from your VCS
JIRA activity - pulled from your Project Management tools
There is no way to hide or exclude Git and JIRA activity in Velocity, you will still see it in non-calculated metrics. However, they will be excluded from calculated Velocity metrics.