You can have up to 5 lines on a Koodo account (up to 3 lines until the account is at least active for 90 days).
Each line would have its own plan. They can all be on the same plan if you put them on the same plan while that plan is available.
There are no shared data plans @Koodo. Only Rogers/Bell/Telus offer that. Hey, the bigger brands have to save something for themselves :-O
If your lines don't include unlimited nation-wide calling, calls between lines on a given account are unlimited.
Hope that helps.