I can’t say enough good things about the high neck “wug” style cut. This cut works well on both of my horses(OTTB), one of which is extremely narrow through the chest/shoulders. I have used both the Rambo Wug and the Weatherbeeta Freestyle High Neck and both have fit “Mr Narrow” well. I think Smartpak makes their Ultimate in a high neck style, and Dover’s Northwind also comes high neck. You can also find Weatherbeeta high necks that aren’t the “Freestyle” cut for about $100. My favorite thing about these high neck blankets is that the rain/snow/sleet doesn’t drip down inside the blanket. I have never had one of these cuts rub shoulders and they don’t slide back (used 3 seasons).
The Rambo has held up very very well, and one of my guys is a destroyer of all things blanket. The Weathrbeeta Freestyle has held up OK, and my barn mate got the regular high neck Weatherbeeta, which already has the tail flap torn off after being worn 10 times. Another feature I like about the Rambo is the angled front snaps, as I feel this doesn’t “choke” them as much when their head is down grazing. I also like that it has 3 belly straps and a tail cord instead of back leg straps, and I have never had a blanket shift. I have never owned a Rhino or Amigo, but they have similar features for a lower $$$. PS-order Rambo or Rhino one size smaller than your typical blanket size as well as the Weatherbeeta Freestyle.
Sleezy, or lycra, shoulder guards and Bossy Bibs are also an option. I hear great things about the Bossy Bibs but they are kind of hard to get. I have used lycra guards in the past, but they weren’t completely covered by my turnout in the neck area and got wet when it rained/snowed 🙁