I’m sure over the years they have managed to make wide boards ride a little narrower
This is true to a certain extent. I currently ride a 168W Split, a 164W Twin and a 163W Directional. They all ride better than the wide boards of 10 years ago. But then so do most boards …
The width of the narrowest part is only part of the picture but the chances are if it’s wider than you are used to in the ‘waist’ then it may well be have a sidecut/radius that makes it harder work to go from edge to edge.
In many respects it’s perhaps easier for a ‘bigfoot’ rider to ride a narrower board than it is for a smaller foot rider to ride a wide board – especially if you mainly want it for carving on the piste. Many modern boots have a smaller footprint these days and it also very much depends on your angles and stance and whether you can effectively pressure the four ‘corners’ of the board.
But yes … a few mm here and there and 3 degrees plus or minus can often make a real difference on a snowboard – more so than on a bike I reckon. For sure a good rider will be able to adapt to pretty much any board, but is it worth the risk spoiling an annual trip on the slopes by buying a board that isn’t fun for you to ride?
Shame you can’t demo the board