I’ve played with quite a few optics combos but haven’t jumped on the 12x fad yet.
Spotter will completely depend on your terrain and what you hope to achieve. With 10x on a tripod I get a pretty good read on the frame size of an animal from up to a mile. If I want to count inches/get a really detailed look to decide if it’s what I’m after a spotter is invaluable.
I’m always in the Rockies on a peak glassing where I can see for hundreds of miles or in the plains which is wide wide open.
I’ve always found I want more magnification.
I tried the 15x tripod combo once to see if I would miss a spotter. I did. The 15’s have they’re place but not a do all. I suspect I’d be the same with 12’s. Just picking them up in a store I can’t hand hold them.
I always run 10x42 with a spotter now.
I’ve tried the small ones as I’m a weight weinie.
The best compact for me was the leupold 15-30 x 50. Better view than the razor.
Now a days it’s worth the weight for me to pack a 65 as a minimum. The extra light gathering, field of view, magnification and better clarity offset the extra weight for my needs.
Something else to consider is that a small spotter won’t be as good as the view in your binos in low light and they all get very narrow, dim and hard to see through at max zoom.
Count on a useable magnification around 20x for most of the compact spotters in the lower price range
TLDR; Spotter will depend on terrain and your goals. In my experience bigger is better.