Heyo,
Chiming in on this as I have personally been involved in majority of the programs on offer before joining WG in an official capacity in which I now manage some of the program.
Firstly; information on majority of the programs can be found in the Community Programs Section of the forums which gives a broad overview of the programs and their intentions.
Onto your main questions:
All of these programs are volunteer based, participants are not paid nor employed by Wargaming. They are selected for programs based on their activities in and outside the game and are offered the opportunity to test WIP content and provide feedback on it. In some programs they do get to keep the ships after testing and have access to items for giveaways. Some programs, participation in providing feedback through either written, verbal, or gameplay means is a requirement to remain active in the program, others it is more voluntary in nature.
This is a somewhat loaded statement. Whether a ship is OP/UP/Etc is very subjective in nature, all ships are designed to have their strong points, and their weaknesses. Smolensk is a great example of this, while it does have high RoF and fire qualities, it suffers in close quarter combat and has an extremely susceptible armor scheme to counter its strong qualities. All community program participant data is used in determining early trends / stats of the ship, and consideration given to the general "feel" of the ship from participants. Opinions are often varied on the quality of a ship offered some finding it good, some not. Speaking from experience from being a ST, many changes to ships often occur before the ship even makes it to live server testing. It would be unfair for me to comment on how participants may feel when it comes to their feedback being taken, but I can confirm we do take it and use it.
While I can't make comment on actions taken specifically from particularly participant feedback, I can assure you that we do listen and act when appropriately - and this isn't limited to feedback from program participants alone. Some key examples of us listening and revising based from Community and participant feedback include:
Giulio Cesare rebalancing: Decision was reversed to amend this premium ship based on community feedback. Follow on decision to not touch premium ships after release beyond game wide mechanics changing.
Original NTC concept: Scrapped completely based on community and participant feedback. Redesigned with out ship bonuses.
Priority Sector system: System was redesigned completely to be more interactive based from feedback that the old system was clunky to use and ineffective.
I hope this helps with your perceptions of the programs and their intentions.
Fem,