Grid2 works in WoW Forever. There's no separate Forever download: the main release includes Forever, and its TOC file lists Forever's interface number, 16001, next to Retail's. The latest release is 4.1.11 from 9 November, so it's being kept up during launch. We checked its GitHub repository on 10 November.
What Grid2 does
It replaces party and raid frames with a compact grid of boxes. Each box can show health, missing health, debuffs you can dispel, aggro, range and the buffs you care about, through indicators you place yourself. It looks plain until you set it up, and that's the point: you add only what you need.
Setting it up
- Install it like any add-on. Our install guide covers the folder.
- Type
/grid2to open the options. - Start with the layout for your group size, then add indicators one at a time: dispellable debuffs first if you heal, aggro if you tank.
- Hide the default party and raid frames once Grid2 shows what you need, or you'll have both.
Click casting
Grid2 doesn't do click casting itself. Pair it with 
Clique, which got a Forever file on 8 November, or use the game's own click casting. Our Clique and click casting page covers both.
Grid2 or something else
VuhDo if you heal and want frames plus click casting in one add-on.- HealBot if you want something that works well before you touch a setting.
- Cell has no Forever version yet.
Best healer add-ons compares them, and Grid2's add-on page shows our latest check.