OK, back home now typing from a real computer! A few follow-up thoughts.
The first is that everyone is different when it comes to both perceiving tone and accepting or being frustrated by differences in tone between two rigs that whether they are significant or insignificant depend less on the differences themselves than the hearing and sensibilities of the listener. Myself, for example, I long ago stopped caring about minor tone differences that are apparent primarily, if not only, when playing alone in my room. I've simply come to the personal (as in, works for me, not necessarily anyone else) realization that the people I'm making my music for to bring them joy are just not picking apart my tone, they're digging the music. So that's my starting point. Whether it unduly colors everything else I add below is up to you.
Here are my SMS and RV300 settings (not including the rear trim pot which, if I'm recalling correctly now, is around set around 1-2 o'clock. These work for me, with my guitar (Philtone Jerrycaster - I live primarily on the middle Super 2 split) and my effects. They might not with your guitar and your effects. That's why, while I'm happy to share my settings and enjoy seeing others', anyone else's preferences - even Jerry's! - cannot, in a vacuum, substitute for your own. Note also that my SMS and RV300 settings are cumulative. A change in any control on one necessarily affects the other. I settled on my own preferences after months of experimentation, changes, more experimentation, more changes, etc. Some people may "know" within minutes what they prefer. That's cool. I kinda wish I could. But it's not me. I need the data that only multiple practices and gigs can provide to figure it all out for myself.
For me, my Reactance and Definition controls roughly parallel my bass and treble controls: the former way down; the latter way up. I can tell you that this is not
how I started out with my RV300. I came in with the preconception that the former should be higher and the latter lower. But that's not what my ears told me and I know well enough by now to trust my ears, not my eyes.
You'll also note that the volume levels on the two RV300 channels are set quite differently. That's because each side of my RV300 is driving a very different type of speaker. The side with the volume up higher is driving a Weber Neomag. That's my "main" tone. The other side with the volume lower is driving a Jensen Neo 12-100. That's my secondary tone. I use it to compensate for my perception of the Neomag's weakness - that while it has wonderful treble and upper mids, it's whimpy on the lower mids. The Neo 12-100, in contrast, has robust, really filling lower mids. So I set the Neomag to the volume I need at the time and bring up the Neo 12-100 just enough to yield the combined fuller tone that I prefer.
This is all, to repeat, just a box of rain. Believe it if you need it.
"For me, I think the only danger is being too much in love with guitar playing. The music is the most important thing, and the guitar is only the instrument." Jerry Garcia