Will a lid from one bottle fit another?
Yes. One thread runs through the whole range, which is why a spare lid is listed once rather than eleven times.
How do I clean the insulated bodies?
Top rack of the dishwasher for the body, hand wash for the cap so the gasket keeps its shape.
Is the titanium bottle insulated?
No. It is single wall. You choose it for weight and for taste, not for temperature.
What does the warranty cover?
Manufacturing faults for five years. Gaskets and straws are wear parts and are sold as spares.