It's not a simple question. So that others can offer informed suggestions; you may want to provide more information. Such as:
- Your router model
- Firmware version
- Are you using AiMesh
- What existing Add-On scripts are you running
- What performance issue(s) you are trying to address
- What security issues you are trying to address
- What previous steps have you taken for performance and security
If you haven't done so already you should see the pinned/tacked
Asuswrt-Merlin Addon Software Catalog thread for the various add-on scripts and read about the one's that you think or feel you need to use for your environment or situation.