I want to lubricate the moving parts on the convertible tops on 2 cars (a
BMW Z4 and a Mazda MX-5).

Neither manufacturer seems to provide any guidance on this matter, and the
various relevant forums have thrown up a mixture of suggestions to use (a)
Lithium (b) PTFE / Teflon or (c) Silicone based lubricants.

Which should I use, or does it matter?