What relics are better for you will more often than not depend on the play style you have. Try to think of it like this: if you’re casting a lot of Chain Heals a Floodwater relic will be more useful to you than say Buffeting Waves. This is assuming you have a choice between different relics, generally speaking, a higher item level relic is better due to the fact that increases the amount of Intellect we have. Empowered Droplets is generally always useful unless you’re only doing dungeons.
Of course, if you have a lot choice you can play into strengthening the legendaries you have already, though since you might have several and may change them depending on the fight I would argue it’s a safer bet to look at what spells you use, what content you’re running and play into those strengths.
If you’re wondering which two to choose from specifically you can always ask here or hop onto the resto channel in the shaman discord Earthshrine and ask there, there’s usually someone around to give and answer. I hope that clears things up a bit.