Processor Speed and diagnostic test

Hello. This is just a general question nothing is wrong with my computer. I am wanting to run diagnostic test and processor speed tests. What would be a good program for me to use to do this in general across all processors as I also help my friends with their laptop programs. I have found this one (have not installed as of yet) https://cpu.userbenchmark.com/Software. I have used this site when comparing processors as they have nifty charts that compare processors against each other and have found no problem. I however have not been able to find a diagnostic tool. Currently I personally use AVG driver update to find drivers that are out of date and I go to the products website to download the driver. I don't exactly trust downloading from 3rd party applications, I just use the antivirus as an extra line of defense and I have all these other applications I can use with my subscription so took advantage of that. I know Windows Defender can do this which is what I use and may continue using with my friends laptops. The 3rd party applications will solely be downloaded to a flash drive as well for portability. Thanks!