Hiya, welcome to Purrs! I am now coming to the end of my adoption story, I am hopefully bringing my 2 new friends home tomorrow afternoon! Originally I really wanted kittens, but I am having 2 6/7 month old siblings instead as both myself and my partner work full time, and even though he works shifts, they would be left to 4-5 hours most days. I would suggest that you look for cats 6 months or older as you will be out for most of the day. Siblings from the same litter would be ideal, but 2 cats who have always lived together and enjoy each others company can be just as close.
As far as travelling goes, my last cat did not travel well, on the 1/2 hour journey home when I picked him up he had every kind of accident going and the car smelled interesting for a few days! Every time he has been in his carrier since then, he has usually at least peed in it. Some cats, however will be much better travellers but it is really up to individual animals. Once you have found your cats and got to know their personalities, you willbe able to judge much better what is best for them.
Good luck!