I believe Huki skis are generally known to be very well made and very well designed/engineered. Small company where boats are made by, or at least overseen by, the owner himself, in California. S1-R is comparable to V10Sport, stability-wise, so very stable for intermediate or advanced paddlers, probably fairly tippy for beginner. I think Huki seats tend to be somewhat narrow, but can get wide seat option if you have wider hips. I also think of Huki as a bit more expensive, but warranted. Jude, the owner, went into great detail with me at the Gorge race as to why the S1-R surfs better than others, so maybe that helps on your 3rd question. High quality boats.
KR McGregor Rhythm, V10Sport, Swordfish S, Fenn Tarpon S, Fenn XT, Twogood Chalupski, Findeisen Stinger spec. Had: V12, Stellar SE, Huki S1-X, Burton wedge2, Fenn Tarpon