This needed a bit of a dish, as I’m getting rather excited about it. 
It has taken me a while to start digging in to the Neural Amp Model Module, but now that I have started, I’m really digging it. Thank you so much @JamO for including that as a standard Module that can work in plugin mode !!!
For “guitar amps” and “bass amps”, I’ve had great luck so far going the simple route, finding perfectly acceptable-to-me models that are amp-and-cab style, but at some point I might try the separate amp model and cab IR route (too many other things to do in the meantime). At any rate, that alone is pretty momentous–especially having the specialized tone-stacks available like that; what a difference!
What I’ve really been excited about, though, is the NAM models that are acoustic simulator or acoustic instrument models, then paired with an instrument IR. I’m still experimenting of course, but thus far I’ve been pretty amazed at how decent a sound I can get from a pretty standard Strat.
One such patch has one Chain running two NAM models (first an acoustic simulator to improve the string sound, then an acoustic guitar model to get more of the body), followed by a Cabinet Module with an instrument IR (which brings out some dimension); a second Chain then uses a “distant mic” NAM model without Cabinet, at reduced Mixer volume, to blend in a little more space. After the MG3 plugin, a different plugin adds a little compression and not-very-much reverb.
That one was the eye opener for stacking and blending. I’m still working through the best way to approach a 12-string-sim sound (using MG3’s Transposer on a second Chain for the 8va); the basic idea is there and sounds pretty good in the middle register, but the trick seems to be in taming the “tinny-ness” of the upper register. A much quicker hit was a single NAM model for Dobro, paired with one of a couple of different IRs for resophonic guitar. That one’s fun!
None of these are perfect, of course, but if the idea is to be able to be playing standard electric guitar, then [stomp] playing Dobro, then [stomp] playing SWAM cello, etc., without changing instruments, then this is getting me some pretty spectacular mileage in that direction.
Hopefully more to come, but this has now given me yet another reason to appreciate what MG3 is capable of doing.