On one of the questions it referred to " a lot of luggage" regarding the shuttle from the economy parking. What is considered "a lot"? I will have three suitcases, one of them being being a sport tube 14"x10"x50" long.

You got this they are very helpful to make sure everyone gets to the central part of airport

Since you might not be the 1st person on the bus the sport tube will likely be along the luggage rack on the floor. If there is a mess, the bus driver will help sorting all.

You'll be good.

They have two racks for luggage that can probably hold ~20 suitcases. You should be good.

They should accommodate