Yes, it will cause inconsistency. You aren't shooting the cb to the pocket. You are always, unless doing a masse' shot, shooting the cb down a straight line. That means you want your setup to be the same every time you can.
Ideally, you want your eye alignment, your elbow, your upper arm in line with the cue. With your hand freely hanging straight down. And, you want to be able to stroke the cue with those things staying in line. If you can do that, and are set up like that, then your cue will stay on the shot line throughout the stroke. Any variance off that means that you will at some point be steering the cue to stay on the shot line, or will actually steer off the shot line at some point.
If you have a home table, and a mirror, line up like I described with your arm over the cue. Now, move your front foot and see what happens. While it is easily possible to move both your feet one at a time without changing your upper stance position, you will find that what usually happens is your hip moves with your foot movement. Moving your hip means your upper body just moved off the correct line, and you now have to be very careful because you will have a tendency to steer the cue.
What you want for foot placement is what allows you to have the upper body positioned correctly. Then, do the same thing for every standard shot. If you have to reach, you usually have other body parts on the table for support and alignment, and then the feet aren't as critical.
For most people, the above means that your back foot toes will be on the shot line, and your front foot will be parallel, or slightly turned out from parallel with your back foot. And your feet will point close to 45 degrees from the shotline.