Being on pasture is fine for a mini. Just be sure they are used to grazing. If the mini has been in a stall, the mini might overdo the grass and get colic or founder. Those are two things to watch for.
Minis are very hardy little horses. In the winter they grow very long, shaggy coats to withstand the cold.
Minis are extremely smart and clever. They are personable and loving. Each one has a personality to love.
Minis are more curious, IMHO, than big horses and do not seem to spook as much as the big ones. At least that has been my experience.
Big horses are often afraid when they see a mini, but a mini doesn't seem to be afraid of big horses. Minis are big horses in a little body.