[ernopp]

I just hope there won't be too much of a performance impact on my browser or the page load times

[posobin]

IIUC the content scripts that extensions use load after the page is loaded, so this shouldn't affect page load times. But please reach out if you feel like it does!

[modeless]

Most pages these days still do a lot of additional loading after "page load", so you're still going to be delaying that unless you take special pains to wait until all other JavaScript activity has died down.