Cannible,
The private sub-forums work like this as of now:
And as far as security to private Sub-Forums, so far I have it planned out like this: Since one of the features in both packages is your clan gets its own member group, I'd set the restrictions to that Sub-Forum to only allow members that are part of that member group to access it.
However, if you would prefer the sub-forum password-protected, I will look into that and see what I can do.
To your second question,
The achievements are planned to be weekly as described in this:
It is planned that every other week an achievement pack for Gold subscriptions and the weeks in between will have achievement packs released for Premium clan memberships only.
To your third question,
It all depends on what base you would want, gold or premium. That will determine the price. The reason for this is that I plan on releasing more features in the future that would be split for gold/premium memberships (premium obviously getting the better side).
Another alternative is this for prices:
-Base Price: 5k
-Private Sub-Forum: 7.5k
-Moderators: 1k each
-Public Sub-Forum: 5k
Then, to access certain features for gold/premium memberships, you are suggested to pay for one of these.
-Gold: 4k
OR
-Premium: 8k