Thank you for sharing your view N8H! I am not a resident of Idaho, but have family here and have been hunting here for the last month, so while I am pretty familiar with the issue, I haven't heard from many people in support of it and am interested in that POV.
The open primaries is certainly the more appealing of the two. I think the benefit of open primaries is that it prevents the primary from becoming a race to the far ends of the respective party (which has caused a lot of bad candidate recruiting by both parties). It instead allows the most likely candidates to rise to the top and give voters better choices in the general election.
On the other hand, I think there are some issues with RCV (especially in how it is generally being used to take seats from Rs/the majority party, see Alaska), which is what makes prop 1 unlikely to pass in Idaho (just my guess). In my personal view, it just depends on if you care more about the open primaries, or helping the R party nationally and ensuring Rs (or whatever the majority party is) don't split votes while the minority party mass votes for one party.