This is my all-time favorite bonefish fly..
It's basically a McVeigh Gotcha but with a tan arctic fox wing and fluro hot red head (instead of pink). You can find the basic dressing on loads of sites. I use this fly in sizes 4 and 6 in the Bahamas.
The following is my favorite for Barracuda.
This is an elongated surf candy (Bob Popovics pattern). The ultra hair stands up to Cuda teeth better than most other materials.
Those are two personal favorites which I would fish with confidence in most locations. I would drop the guys at Hardplay an email for any specific local recommendations suitable for the time of year you're visiting. If you're fishing around reef structure a collection of clousers in various sizes and colors would be a good bet.
Good luck and post your results!
Leaders tend to be an emotive subject so any advice is given "under advisement"
For bonefish, I like a minimum of twelve feet tapering to a 10lb flurocarbon tippet. Most of the fishing is sight casting with floating lines - your 8 weight should be perfect unless the wind is really strong.
For Barracuda you can get away with a shorter leader - I use about 10 ft of 15lb fluro straight through with a wire shock tippet about 10 inches long connected with an Albright knot.
I've never fished for tarpon but shock tippets are recommended. They have no teeth but the scales are very hard and will wear through regular leader materials. The newer hard fluro stuff may stand up better but I would go with local recommendations to start with.