A drive doesn’t need to sound fizzy by definition- for all any of us know there is already some filtering of the high-end in the drive signal chain (the clips I’ve heard certainly don’t sound fizzy to me, even if I haven’t heard anything particularly to my taste in them yet) and the High band sounds plenty powerful in the Navarro demo to eliminate any fizziness (in fact that may be a great argument for the particularly high voicing of the High-mid band, as you could bump that up while dropping the High shelving control and get a pretty good cab-like resonance up top). The Tone switch attached to the Drive circuit may well also be adding some variable high-end filtering.
I actually generally stray away from IR cab-sim personally. I have found through lots of trial and error that it usually just doesn’t sound particularly good to me, and there are too many variables involved when making an IR to really nail the sound of any particular cabinet (people often forget that there is the whole mic effect involved in an IR, just as there is in a studio or live show that can make or break a miced cab tone- and the tech used to make an IR file is hardly recreating all the variables of what a cab gives you anyway. It’s like a monochromatic painting of a cabinet sound). The beauty of real cab tone is a 3-dimensional stereo thing, and no IR loader will give you that through a simple mono DI- why even rely on that kind of funky and limiting EQ curve if you aren’t playing through a real cab? I much prefer my own EQ curves to accomplish “cab-sim” type sounds, and tweaking those is much more versatile in a live environment than some fixed curve that may or may not jive with the room or band mix (so many of the fixed IRs or cabinet emulation curves used on bass pedals are FAR too extreme IME, and have screwed up otherwise fine bass preamps- I’ve felt that way about every Tech 21 I’ve used, the Orange Bass Butler, and a handful of other modern pedals I’ve demoed). I also think adding expensive digital circuitry to a pedal solely for the purpose of IR loading circuitry is a mistake (raising your pricepoint, complexity, and power requirements significantly for something that frankly often doesn’t work as well or as seamlessly in a mix as many people want it to).
I’ve been playing with driven amp and pedal tones for a few decades and definitely haven’t found my live PA tone improved greatly by any fixed cab-emulation circuitry from a pedal I’ve tried yet. In a live environment I get what I need with some high-cut and usually HPF of some sort (not always necessary if not using a stage rig, as the board often has it too), in a studio basically every DAW has preset cab circuitry that sounds at least as good as what a basic pedal might do at least for monitoring purposes, and you aren’t married to a particular tone after you’ve recorded it as you would be with a fixed tone in an outboard pedal. Do I think live sound in general has improved as a result of more of these kinds of “rig in box” ideas so many bands are using? maybe at least it has generally gotten more consistent gig to gig?
Anyway count me in as someone who has zero interest in another preamp with an onboard IR loader (or any unnecessary digital anything) or even a strongly-voiced cab-sim EQ circuit that I will inevitably leave off anyway! Not every new trend is necessarily an improvement across the board IME, and not every new multi-effect needs to compete in the same playing field as a Quad-Cortex, Helix or Kemper. If the drive is voiced as I like it then a high-shelving EQ onboard (as this pedal has) is probably going to be plenty good enough for me to roll off some of the top end.