Is this the upgrade or the base game with expansions?
Is it the base game with all the expansions or just the greymoor expansion? In other words, do I need the base game?
The link you've provided is the base game + expansion :)
This would be the expansion only - https://us.gamesplanet.com/game/the-elder-scrolls-online-greymoor-digital-upgrade-download--1036-18
If you're on the fence with what's contained in each see here - https://gplnk.com/192513reply