I struggle with some of the same thoughts as you, that pursuing further communication or goodbyes while I'm still here is self serving, but I simultaneously believe I owe it to the people in my life and in my past to give them and even myself some level of closure and finality in the form of a note or a last conversation - issue with that being that nothing ever feels adequate.
Thing is, it's impossible to know what will make things harder or easier on the people we leave behind, and ultimately, feeling uncertainty on this topic may lead to stagnation and feelings of incompleteness and inner conflict regarding your decision to CTB (or continue). If you feel the drive to say something or write something - you should. I think you may be doing not only yourself, but the people you're considering, a huge disservice by denying yourself these final exchanges, whether they happen while you're here or after you're gone. If I had someone in my life that CTB, even if we had not been in contact, I would want to understand a bit more, or simply have a final goodbye to help me process or even to just remember - it definitely wouldn't make things harder for me personally.
I think at the very least, you should write something out for anyone you want to address. You don't have to send it anywhere ultimately, but perhaps writing it when the thoughts come will offer some clarity as to what is best to do here. Don't deny yourself direct exchanges while you're still here, even if the people in question don't know that the exchange is potentially a goodbye. Ultimately, it's okay to be "selfish," this is your life and your death and you deserve to feel complete. Of course, worrying that you might say too much or worry people, or that you might be stopped in your plans is something to consider.
I really hope it doesn't come to that, for what it's worth.