I’m alllllll about the v snap front, too. The only blankets I’ve found with it other than Rambo are Busse, and bought this one last year to try it out:
https://www.equishop.com/en/winter-horse-rugs-up-to-500-gr-or-more/31543-busse-flexible-pro-250-horse-turnout-rug.html
(Here is a 50 gram version and hmmm, I’m not sure if the Flexible Pro comes in a sheet, but they make others that do.)
(Oh they’re on saaaaaaaale!)
Obvs not an Optimo dupe (although I don’t find these Leaders blankets to be like Optimo either? It looks like a pretty standard shoulder dart rather than what Optimo has, all the way to the spine and behind the shoulder) but a very nice alternative to Rambo. I took some pics and wrote about it when I bought it here. And I had no rubs with it, just like Rambo