I'm glad you like our "feeling face" chart! We've found it to be really helpful in teaching our toddler to recognize and identify different emotions, as well as giving them a sense of control over how they're feeling.
In terms of preventing tantrums and meltdowns, I think the emotional thermometer has been really beneficial. By encouraging our child to rate her emotions on the scale, we've seen that she's more aware of when she might be getting overwhelmed or frustrated. This allows us to intervene early and help her calm down before things escalate.
One benefit we've noticed is that she's becoming more able to articulate how she's feeling in a given moment. She'll say something like "I'm really mad on the 7" which helps us understand what she needs from us in that situation.
It seems like you're already on this track with your own toddler! Do you find that the visual aid of the emojis is helpful for her to remember and identify emotions? We've found that our child responds well to seeing pictures, but it's also good to explain the concepts behind them. Does she have a favorite emoji or one that she tends to use most often?'