OK, looks like you got some responses.
Here's your original post, I'll try to work on each section individually:
I have regular Drake fins and been told if want to increase performance in terms of speed need specialised fins for that purpose.
There is many fin brand/type. Select;Deboichet.Tectonics,Maui etc.A pro windsurfer recommended me strongly Tectonics Talon fins.
1-Are Talon ideal type of gear for my equipment or other type of tectonics or any other kind fin suits most?
Tectonics are certainly good, and the Talon is just one model.
Looks like the Talon is Dennis Partons "latest and greatest" but you need to get on a waiting list to get one.
Since you are not racing slalom at a pro level, I think some of the other Tectonics fins might work almost as well, without the wait.
Try one of Wolfgang Lessachers 15 deg. LE fins. If they are anything like his Duo assymetrical weed fins, they will be fast and you probably won't be able to spin one out.
2-What fin length should be for above board and sails as I am planning to buy 2 fins for each board?
If you plan to use the stock fins in your quiver of fins, I would look for a fin 4 cm smaller and 4 cm larger for each board.
Smaller is to go fast in windy conditions, larger is to get planing earlier when the stock fin won't quite get it done.
For the time being I am stuck about 30 knots max .It is the limit I could not pass beyond last season.I expect with Futura I could achieve 33-34 knots at least.I was using F111 with Drake 38 fin.Maybe need a smaller one?
30 knots on a 38 cm fin is pretty darn fast. I'd try a 34 and 32 on the same board with half to a meter smaller rig.
3-Last confusing topic.Read somewhere that on same conditions using no cam instead od cam sail you have to rig 1-1,2 m. smaller in order to sail without owerpowered.E.g. sailnig V8 7,5 m comfortably and if you want switch nocam ( NP Solo) you have to use 6/ 6,5 m.
This "ratio" (1-1.2 m2 smaller) does not make sense to me.
I agree with Ken, a well designed no cam (like the Sailworks Retro) can be sailed pretty much size for size (this has been proven many times on race courses in the Gorge).
Other brands may differ, and a good 4 cam top of the line "no expense spared" race sail will definitely be a little more stable and user friendly in really overpowering conditions or when you want to go super fast.
I know cam sails are more forgiving during gust and covers a bigger windrange without changing the sail vs nocamsails. but is the difference really such big?
The wind range is actually better overall on a good no-cam like the Retro. It has a wider tuning range and can give you much better low end power that a dedicated race sail because it can be tuned for a greater range of conditions without taking away from the top end performance.
I have a Hellcat 7,2.In that sense what is the equivalent cam sail of my 7,2?
V8 7,5/8.0/ 8,5 ?Could not get any satisfactory answer experienced windsurfer around.
No one can really answer that question...... It totally depends on how you rig the sail.
To the specs, on the right mast, outside the specs to get more top or bottom end.
What ever you do, the range is not going to be much more than 7.0-7.5 equivalent.
Hope this helps,