Well, boosters don't necessarily yield more trebel but they do remove a significant amount of bass and low-mids, which gives the impression of them being brighter. This could also lead to a perception of a "thin" sound. Listening to the guitar tracks of your album I can sey they sound awesome but every guitar is a different world.
So, would you classify the Emerald and Rebel Yell warmer or fuller sounding than the higher output ceramic models? The EQ charts on the website clearly lead to confusion as they don't have any relationship with other pickups. How would you compare the Emerald to the Rebel Yell?
What boost pedal do you use? I'd recommend checking out the MXR GT-OD, Maxon OD9 Pro+, or Amptweaker Tight Drive for very tweakable boosts that will not leave your tone sounding thin or overly bright.
I wouldn't call the Emerald or Rebel Yell fuller or warmer, but their extreme top end is smoother. In general, the hotter the wind, the lower the resonant peak of the pickup, so the hotter ceramic pickups are quite full in the low mids but still have the characteristic ceramic glassiness to the top end. By contrast, the mid output alnico pickups have higher resonant peaks that give them their punchy upper midrange and lean low end character.
The Emerald is a brighter and tighter sound than the Rebel Yell, with a more open dynamic. I would generally reserve the Emerald for 7 and 8 string usage, moving to the Rebel Yell for 6-string if you want a very similar character with more chunk to keep the higher tuning sounding powerful.
Yes, the EQ charts can be confusing; Tim was reluctant to include them on the website, but it was one of the biggest user requests so they were put up.