The luggage policy may vary between different operators, so it's a good idea to take a peek at the booking info page for the ride you've chosen. Once you've selected your preferred option, you'll be able to find all the details right there.
Generally speaking, most operators have similar policies when it comes to luggage, what is usually allowed is one regular-sized suitcase (around 23 kg) and 1 piece of hand luggage per person.