My friend has a COSORI, and it feels really low quality to me.
Every Fellow Carter product I've used feels much better quality. It also has precise temperature and can hold it's temperature as well.
I would recommend the Fellow Corvo over the Fellow EKG for tea. The Fellow EKG is great for a V60 pourover coffee, but it pours far too slow for tea.
The ones I see most often recommended are...
Bonavita (I own this one and have brewed a lot of tea with it)
Fellow Stagg (very similar to the Bonavita)
Fellow Corvo (similar to the previous ones, but not a gooseneck so it has a faster and less precise pour, but also pours slightly hotter as there is no spout to drain heat from the water)
These are all going to be very similar in practice, but the Corvo may edge out the others for gongfu brewing (faster pour, hotter water), if that's something you are into.
I recommend the Fellow Corvo for your electric kettle
What I use is a cheap variable temperature miroco gooseneck kettle. My advice is to get one that isn't gooseneck for a faster pour if you're gongfu brewing puerh, or pour from the top and not the spout(this is what I do). this corvo ekg I think would be a better choice, or it's what I would have gotten had I known.