What size of the mat is best for sleeping? Can I sleep on my mini mat?

You can sleep on the Mini mat, and it will warm you up, but the size of the mat really matters. 

The smaller mats are not so good for sleeping because a small area of your body is elevated over the level of your bed mattress. You may feel uncomfortable.

Usually, the Compact Pro 24"x59" model is OK for shorter people, but the professional mat 29”x73” is a better choice for tall people. Of course, the Single size mats 39"x75" are the best for sleeping.

Queen mats are very rare and unique; they allow to adjust heat levels separately for the left and right sides of the mat. It is the best choice if you share your queen bed with your spouse.