Could you please provide us following information regarding your query?
1. Did you mean 20+ elements as referred Grid columns or records in Grid?
2. Do you want to specify the columns for Grid by using ngFor?
3. Do you need render the Grid with header template?
4. Please provide clear requirement.
5. If possible provide the screenshot expected output.
It will be great helpful for us to analyze about the issue and provide you a response as early as possible.