I can't offer any insight on the coils but I have Timbrens on my truck and I think there's pretty close to an inch or maybe a hair less when you install them without the included spacer. This is on my 2015 2500 which should be the same as your 2014. I can discern no difference in the unloaded or "family loaded" ride (2 adults, 3 kids, 60 lb dog and assorted luggage for a weekend trip).
With about 2600-2800 lbs on the rear axle or maybe a bit more the coils sink enough to contact the Timbren but only lightly with no visible deflection at all. The loaded sag is actually no different or barely different than it was without the Timbrens, but the Timbrens definitely firmed up the ride going down the highway. I mean that in a good way - I think they work great. I don't like airbags especially on a truck like mine that spends time offroad, and I was drawn to the simplicity of the Timbrens.
Definitely post an update of how the setup works if you go forward with it.
