This is going to depend on if Helix models the mid pot as linear or audio. The log/audio mid pots on a BF amp need to be around 9 to give 6.8k of resistance to match the amps without a mid control. I see a lot of people trying to run just below 7 to match the 6.8, but that will give you less gain and less mids, unless it is a linear pot, or a model of a linear pot.
Yeah, I know Line 6 has said to set the knob at 6.8 at some point or another, but I don't remember if that was for all of the relevant Fender amps, or just for a specific model. Either way, it was just as a starting point / reference, and I was finding pretty consistently that the mid knob had to be quite a bit lower on Helix to match the captures. Interestingly enough, I remember people here (I think) saying that to match the Helix Deluxe to the UA Dream, the mids had to be pushed quite a bit.
And of course these tonestacks are so interactive; I think some of what I was hearing was the mid range sitting a little differently on the Helix models, which I guess is related to the bass and treble adjustments I had to make to match the high and low end.
Speaking of which, the other difference was the high end on Tonex tended to be obviously attenuated when comparing with IR disabled. I think this is the nature of Tonex captures though? Not sure, but it was also pretty consistent in the comparison, though didn't matter much in a real world usage situation, except that I usually needed to push the treble down on the Helix slightly.
Anyway, it's apples to oranges in a lot of ways, but I was mainly surprised that I was feeling better about the Helix Fenders and how they reacted than a few weeks ago lol