Come of San Francisco during the season and I'll take you fishin'
First, I am no expert. I have only been smoking for a year and a half and I am still experimenting.
It doesn't turn out dry but it is firm and chewier than short smoked salmon. I do a recipe that is not smoked as long, http://www.smokingmeatforums.com/g/a/160771/peppered-salmon-for-canadian-thanksgiving/. It is more of a dinner salmon. These are for smoked salmon on an appetizer plate or a snack. These still have quite a salt taste but I don't know about going salt free. I think smoked salmon needs some salty taste.
As for the herb flavours you'd like to add. I would suggest brushing the salmon with some honey that has been heated in a microwave to give it a sticky surface and then put a generous amount of herbs on it. They will stick to the honey.
Keep experimenting and you will get what you like!
Sorry but, I can't imagine only a 20min max smoke. What is your brine and for how long? What type of smoker? How long are you smoking?
Thanks for letting me know how it turned out. I'm glad you liked it.