I'd be more than happy to share with you any information that you want about Saint Bernards....they are my passion.
First of all I want to set the record straight-----Their is no such thing as a dry mouth Saint Bernard. Some can have drier mouths than others, and no they do not drool all of the time. Infact some of them do not drool much at all, maybe only after a big drink of water. But physiologically the breed has loose jowels and this is the reason that they drool.
Another thing to consider is the number one reason that Saint Bernards are rehomed is because of their size. You have already indicated that you were worried about the size of the Saint/BC X. So you have to ask yourself what is the biggest you are comfortable with a dog getting. A Saint/BC will not be as big as a pure Saint but will still be a big dog, especially a male.
Saints may not be the brightest breed, but they are easily trainable. They are very eager to please their owners. The reason that their is such an emphasis on training a Saint is because an unruly 100lb puppy can cause a tremendous amount of damage and problems. Some Saint owners and breeders will say that Saints are very intellegent dogs. But I always joke that the only thing that isn't giant about them is their brains!
Also, keep in mind that a Saint is very prone to joint issues. The health history of any Saint or SaintX is important when considering the future health of your pup. The last thing you want is a 100lb dog that can barely walk when it is 4 years old. it is heartbreaking and can cost you into the thousands.
Either way, whatever you do get I can't wait to see pictures!