I don't recall if I went from 4.2 or 5.0 to 5.1. I've gotten rid of everything older than 5.1 out of my four slots now since I'm confident in 5.1. Probably 5.0 if that was the previously released version.
You're right to be cautious since I prefer, in general, not to pass forward old configurations to prevent corruption. Live on the edge. Keep your current system in a slot (and on a USB stick) and go for the auto-upgrade. You can always go back. If it works, it's nice not to waste all that time configuring from scratch.
I
did restore my settings from 4.2 (which image I've been using for a few years now), and everything APPEARS to be working fine. Though, I also recently started playing with another OpenVix image for the first time in about 5 years, and in just a few days of playing with that, and then coming back to TNAP 5.1 it seems like going directly from High school back to Kindergarten, lol.
The biggest difference I noticed, is, remember WAY back when ALL the early TNAP images before LATE 4.1 image would jump time/not keep time at random while in Standby, and EB finally fixed it for well and good in TNAP 4.2? That would cause HAVOC with record timers, because it would jump back at random to 1969 or 1970 Epoch times.
Well, the latest OpenVix 6.6 from this year
STILL has that problem! I installed the HWCLOCK missing linux file mentioned in a thread at Legit, and it settled down quite a bit, but still does it. Haven't been able to figure out as of yet what else needs to be tweaked to get it to stay correct.
TNAP 5.1 stays rock steady on the clock, Standby Mode or not.