@dannyswift Chrome should automatically hibernate extensions if they're not in use, except for "persistent" background extensions.
As for your request, you can set this behaviour yourself:
Go to vivaldi://extensions
Find an extension you want to limit to work on click only
click "details"
Scroll until you find the "Site access" choice:
defd6452-08c5-4679-9c25-65150aeaa9cb-image.png
Set it to "on click"
Then, that extension will only activate when you click it's button.