I think a good example of @Chiquinho statement is Life q35 and the Life tune Pro are basically the same earbuds but with different names. It is believed in past threads that the two different sets is one set is purely store sold and the other set is a purely internet sold set. It seems to be more of the Life series that have the duel sets of devices with different name.
I always looked at the different types as of functionality of the earbuds based on their naming.
Spirit series seem more outdoors, workout and sweat type earbuds none with app support
Liberty series was the more their signature buds with awesome sounds with app support
Life series seems to be the functions earbuds (noise canceling/noise reduction/ bass up) with app support
If the earbuds follow this type of format, I am wondering if the Liberty 3 Pro (that people are thinking are being made ) will have NC functionality that people have been asking for the Liberty 2 Pros and they think it will be in the 3 pro instead or will NC just be in the Life series. (ie Liberty --sound quality Life – NC)
Second question- Which comes first the chicken or the egg? In this case do you decide what type of earbuds you want to build (in ear/on ear/over ear) or do you decide on the functionality before you start the design and that leads to the design. Cause I can see it going either way as you may want to design an earbud that is different from other buds (take the one company that has the bean type earbud) or functionality will lead to what design you can do for the buds.