The only sort of independent test I know of is six years old. It looked at page load times, CPU and memory usage and was published at raymond.cc (
link).
In regard to page load times, most adblockers do well as illustrated with below picture.
The differentiator is the amount of CPU an extension needs to accomplish this job (with so many RAM in modern PC's, memory use is a non-issue) in which Adguard extension finsihed third, behind Ghostery and the winner uBlockOrigin.
There are people complaining about AdGuard slowing down internet speed, but these are usually Adguard desktop users.
My personal experience with Adguard extension is that it works great (even with the Stealth privacy feature enabled).
I use Adguard on my phone with Samsung browser and uBlockOrigin on my PC with Edge browser.