Hey mate I've got the Bomber but it's on a Commencal Clash so I can't compare how it performs with an E160 but I do like it. Bang for buck I think it's amazing. So where to start???
Firstly yes the coil length will matter, but as long as it's for your shock you should be fine. I'm not aware of any coil that can accommodate different length springs. Doesn't mean they don't exist, I've just not heard of it if it does and logically, thinking about it I can't see how it would work.
I've not got experience with the progressive coil. I understand how it works I've just not used one. I don't know how you'd work out which one you'd use. There must be some comparison chart out there if it's significantly different to your normal spring rate. So essentially I'm fucking useless. What I do suggest is call up Cyclinc or MTB suspension centre and have a chat with them. I've had excellent service from both over the years and they've always been bang on with their suggestions for my set ups.