How to tell professors I am not interested in working with them right now, but might want to, later?
You probably know your professors better than anyone on here, as you have interacted with them. Different people respond to rejection in different ways, and this can be a delicate matter.

However, you did note that the professors that you don't want to work with were all responsive to you, which may indicate that they are invested in students. In my experience, faculty who are invested in students want them to do well, and understand that students' research interests will not always perfectly mirror their research interests. Getting a Ph.D. is a long, difficult process, and your professors have gone through it themselves! Thus, they likely know the importance of selecting a research area/advisor that will work best for the student.

My personal advice: Be honest with the professors that you don't want to work with. Tell them that, while you are interested in their research topics/methods, you found a faculty member whose research interests are highly congruent with your personal interests and long-term career goals. You can also tell them that you feel scared that the other faculty member won't take you on, which could open the door for you to directly ask them if they are agreeable to you coming back to work with them, should your relationship with your first choice advisor not work out. Express your appreciation for their responsiveness and for them giving you a chance to work with them.

Some faculty may respond negatively to you, and they may view you as being unreliable or untrustworthy, since you are leaving the projects. I would hope that your faculty will be understanding, if you are able to be open about the situation.

Best of luck!