Here are a few tools that can provide a overview of your org health

Setup -> Health Check, Setup -> Portal Health Check

Setup -> Scale Center

Gives insights on row locks, governor limits etc. Apex Guru insights gives suggestions on which lines of your apex code are using up more resources

https://help.salesforce.com/s/articleView?id=sf.scale_center_overview.htm&type=5

 Setup -> Optimizer

Analyzes your org and provides recommendations

Setup -> Lightning Usage

Get insights on page performance, which pages are viewed the most and the page load times. Login metrics, switches between Lightning and Classic UI etc

Field Trip - Analyze field usage to find unused fields for cleanup 

Value Analytics - This needs Event Monitoring enabled in your org, provides insights on user click-paths page performance etc