Worse than a high soundhole is one that's placed too far away from the last fret. And worst of all is if the space between the last fret and soundhole is filled with a large expanse of unfretted fingerboard. Gets in the way of picking fingers, and has no positive aspect to make up for it.
For me, the aesthetic ideal is a soundhole that's centered precisely at the waist, 12 fret neck, 19 frets total, and soundhole edge between the last fret and imaginary next fret position (the exact location depending on the fingerboard termination style). But most of the time, that puts the waist up higher relative to the neck/bridge than people are used to, which affects playability unless you're standing with a strap. Though personally I think the fingerboard is up a little uncomfortably high with a standard classical guitar in classical position, so my way is better *harumph* But tradition is what it is.
And for fan braced classicals, the usual high soundhole position makes the active area below the lower cross brace more circular, which is probably good for tone. But maybe my aesthetically ideal specs would work better with falcate bracing
As for soundhole size, classical soundholes look too small to me, but the traditional wide rosette style helps to fill it out. A lot of steel string parlor soundholes look overly large to my eye... and sound overly large to my ear. Martin's soundholes look and sound just right.