Yes, both sentences look natural and are grammatically correct. He is smart as well as kind. This means he is both intelligent and kind. It's a very natural and commonly used structure. He is bright as well as warm. This also works well, implying that he is both intelligent (bright) and friendly/compassionate (warm). While slightly less common than the first sentence, it still sounds natural. Both effectively highlight someone's positive traits!

These are grammatically correct, but here are some ideas if you want them to sound more natural: He is both smart and kind. He is not only smart but also kind. He is both bright and warm. I hope this helps!