You'll still mill cards equal to the number of rad counters you have, and you'll still remove a rad counter from yourself for each nonland card you milled, but instead of losing life, you'll gain 1 life for each nonland card you milled
1 Tamiyo's Safekeeping
Now the mana production is amazing but it isn't a way of winning, you need to do something with it and that adds extra components into an already complex brew of synergies
There are plenty of great removal spells just like this that can fit the flavor of any deck that wants them (Eaten Alive for a zombie deck, for example)
Gruul is the perfect color pair for this strategy, as you can play creatures like Mawloc, removal cards like Pest Infestation, and direct damage cards like Crackle with Power
Again, it depends on when you will be getting it it could be within 2022 if you are in North America, otherwise expect it in early 2023