do I need to uninstall the EA app as well and reinstall that onto the external hard drive too
No.
However every source I’ve found online is telling me I need to uninstall sims from the EA app and then reinstall it to my external hard drive
You only need to do this if you are running out of internal storage, it is nothing to do with creating the symlink to the Electronic Arts folder.
The drop down menu in my game library only gives me the option to view properties or manage packs but apparently it should be giving me the option to uninstall the game as well.
Do you not see this?
If you don't see that close EA App, manually trash your Sims 4 base game and Sims 4 Packs folder and empty the trash then re-launch EA App, go to EA App > Settings in the menu bar then download and change the install location to wherever you want to install the game.
Also do I need to move the ‘EA games’ folder across to the hard drive the same as I have done for the ‘Electronic Arts’ folder
No. The EA games folder is the default location where EA App installs games to, unless you change it as described above.
