Welcome BluKat. Gee I'm glad you don't want much!! Seriously though, if you are planning a lot of traveling a giant size dog may not be your best option. I also have a fondness for the giant dogs, but I'm a homebody. You must consider that if you travel your dog would pretty much always have to go cargo due to it's size (unless you're driving everywhere). You don't sound like you have a huge amount of dog experience, but I'm just guessing. Before you buy any dog you need to seriously research and read up on the breed. There's a thread on here about a Great Pyrenee's, which is a guardian dog like a Leo, and there are huge issues with this dog because it's not getting to do what it was bred to do. So remember that with any breed you choose. It may not be suited to a life of travel.
I also don't think a hybrid is a great choice. They should be left to very, very experienced handlers, they come with their own unique set of difficulties that most of us are not equiped to deal with. They are not cut out for life in an apartment or the city. I had a hybrid many years ago (it was a gift to me) and ultimately we could not keep it, he simply wasn't happy with what we had to offer him in a city environment. Our yard wasn't big enough and the fence wasn't high enough!
Cats and dogs are all unique, and no one breed over the other will go well or badly together. That said, any dog that has a prey drive will be harder to adapt to living with a cat. I'm looking for a Malamute right now, but know that unless it's raised from a puppy with a cat it's not going to work out. Prey driven dogs and any cat spell trouble.
If you plan on travelling a lot pick a cat or a dog, but I'd refrain from over stocking your life with furbabies. Good luck to you with that though. I'm sure others will be along with their own opinions. Hope you enjoy the board.