Hi SSSimon
I recently brought my Coreban Edge with similar motivations. I am not really a racer but just wanted something fast and fun for 15km plus paddles along the coast in mild conditions <15not
I have had a few weeks with it now and learning its subtleties. It's most at home in flat water. It has lots of glide and tracks straight as an arrow. Last weekend was glassy and a boat was cruising about 10m to my left going just a little faster than me. I could ride it's wake for little 10 second bursts. Maybe this is called no winding

I am finding foot placement is very important to keep it all working when the winds get up though. I find the wind wants to push the nose around so I move a little forward and lower the nose to keep it going straight. When dealing with wind and paddling across the chop I have started standing well back to free up the nose otherwise I end up doing 100% paddling on one side. Still trying to figure all this out as it's my first displacement board. I would welcome suggestions from anyone with more experience with displacement hulls.
Stability on the Coreban is extremely good, I still haven't taken a swim. I was caught out badly one day by not believing the weather forecast (stupid I know, but it looked so good in the morning). Wind was over 20 knots and the wind vs tide vs reef made the chop real big and messy. It got me home dry but really sore from paddling on one side trying to keep the nose points away from the rocks.
I think if you are looking to do any serious downwinding the other boards are a much better choice. The Coreban will do small stuff as it doesn't bury it's nose like you might expect but the Naish and SIC will cane it on a proper run. If you are paddling the lakes and rivers the Coreban is going to have an advantage as it's very efficient through the water specially upwind into chop.
As boring as it sounds the soft flat deckpad that doesn't put your feet to sleep and the nice handle and bag should be given weight. It just makes the board easy to live with.
Hope that helps a little, Let me know if you have any specific questions about it.
You can't really go wrong with any of those boards. The SIC boards sound tempting. I would love to have a custom SIC one day. I think I am turning into a gear head