Hi Shane, after reading your post (above) I spent some time going through a number of my early morning shooting session results to see if I could find any solutions and answers and will share the following;
ANGLE OF LIGHT
I have looked at my images where I have shot almost directly towards where the sun will rise and where I have shot with the sun rising direction being well out of frame and there is no difference in light affect on the water. Where it will/does make a difference is at the foregrounds and where the shadow is seen.
Simple analogy put a football in the foreground and shoot the scene directly at the rising sun position, the side facing you will be in deep shadow. What I have noticed in all the shots I have done is that there is very rarely an area of shadow on the near foregrounds that can not be dealt with easily if you want to.
SHOOTING TIMES
Honolulu is just slightly more above the horizon than I am below it suggesting shooting durations each side of sunrise/sunset would be similar. It's also only just over 20 degrees from Fiji. It seems that I commence shooting around 30 minutes before official sunrise and give up at about 20 minutes after. In fact I have nothing decent shot after sunrise
In my collection I have images taken from 6 months ago to now and I could not say that one time of year is better than the other but do suspect that there's a greater frequency of good coloured pre sunrise mornings in the warmer months.
SCENE LIGHTNESS
Greg made the comment that your image in post 1 seems brighter than what he would expect for 30 minutes before sunrise and I noted this on a previous shot of yours.
Well, I have an idea. I suspect you are exposing to position the histogram to the right with the aim of getting no clipping/blinkies. So what in fact you may be doing is possibly overexposing a scene and making it brighter than it actually is.
Do we have a situation similar here to photographing a black cat against a black wall where the camera is going to assume things are correct if the cat and wall are grey? I may be wrong but put it up for discussion.
WATER SPEED
I far prefer the shot with less water smoothing and 2 seconds coincides with what I have found best in the region of 1 to 2 seconds.
The ultra smoothy water I consider works better when there is a large area of it and it can become a significant feature of the image, but that's just me
FILTERS
I'm now coming to the conclusion that it's possible to get away with GND and ND filters (unless NDs specifically for ultra smoothing water) if shooting before the sun comes over the horizon.
Hope there's something of use here Shane and look forward to seeing some more. I have just lost my 18-200mm due to a VR problem so itching to get out and try the 28-105 early morning for when the 10-20 is not long enough.
Edit : Set the time on your camera accurately so that you are also able to back check later with the 'Photographers Ephemeris' as to exactly when you took a certain picture with relation to sunrise/sunset time.
Grahame