So brave of you to bring up this subject. I have no thigh gap either, never have, even in my youthful lean days. As a petite woman with thick thighs and muscular calves, I can empathize with you. IMO, it's like shoes and socks, you want the friction to be between the fabric, not the fabric and your skin. Find something, whether bike shorts, tights or leggings, that fit tight but are comfortable. And try them out ahead of time until you find what's right for your style and comfort zone. Pack some of the ointments mentioned, just in case. I don't have Camino experience but I have thunder thigh and walking experience. And please, tell us what works for you when you figure it out!
Btw, ointments will have a petroleum base (like Vaseline) and be slippery where as a cream will not be slippery (and usually washes off easier) although either form may have healing properties for rashes and irritations.