As someone who's also wondering if their X is underpowered, FWIW I'll at least mention something mildly surprising I saw in the manual if helpful. It says to wait 5-10 seconds after the "it's heated" buzz before starting your first draw. I wasn't doing this, and was noticing that my first hits were kinda meh, while a 2nd subsequent hit was much better. I was surprised to see those instructions coming from the 7, which in my case is ready to go right at the buzz. I've also noticed what seems like a more convection lean with the X vs. the 7. The vapor and the roast reminded me of what I see with my RBT Milaana 2: golden brown and extracted, but with no dark/scorching. I was also wondering if the more open draw may have been allowing me to overpower the heater. This was all before I bumped my temps up though, and I also have a brand new battery on the way.
I haven't had a chance to retest a bunch more with: a delay before drawing, higher temps, new battery, and better draw speed discipline/feel like I work towards with convection devices - but I'm hopeful at the moment the X will just be a different, but still good Firewood for me. I'll report back. I'm also interested to see what others hear back - especially if there's more heater capacity that can be "unlocked" firmware-wise.
p.s. If I'm remembering the FW 7 firmware update, I think this was simply to adjust what temps the user/each setting "thinks" are being aimed for, vs. changing the heating profile/capacity, etc. People were seeing charring at supposedly lower temps, so the firmware was changed to more correctly identify (for most users) what each setting was actually hitting temp-wise. For instance if you were seeing char at what was supposedly 420 degrees F before (4 clicks, then 2 clicks on the setting), this was in reality more like 450 degrees. Or said another way, while the original manual listed the top temp as 440, in reality the device was capable or 470. I never sent mine back for the change, and instead just created a table which listed the new temp guidelines for reference.