Like hugging people, I imagine it feels different depending on the recipient of the hug.
For Heimerdinger it would feel cold and emotionally distant while he politely asks what you are doing, and would you please let him go so he can get to work.
For Rumble you’d think he’d be soft and fluffy but he’s actually covered in grease and just slips right through your fingers.
For Poppy, despite her armor it feels rather warm and welcoming if a bit uncomfortable as she holds you too tight.
And for Kled. You’d never know. The last person who tried got his arms cut off and the yordle gnawed off part of his face.