I have used Firefox and about 3 userscripts on Geocaching.com since I can’t remember when. They don’t seem to clash with each other. Very useful to get the webpage how you like it. GC little helper is good.
For puzzles and multi’s where one has changed the coordinates it shows them corrected on the links For online maps…. but I’m not sure which, if any of the scripts does that.
There are also greasemonkey userscripts for other sites to remove adverts, show all logs, etc., etc..
They cannot all be trusted, so take care what you download. GH.