New AEP Mobile SDK migration

Hi All,

We are upgrading from SDK 3.x to SDK 5 the new mobile AEP SDK. Appreciate if someone can help me with a check list of issues/items we have to consider and answer few question 

1. Since we are not migrating from SDK 4.x so can we still use Mobile services extension in Launch?

2. If we use the above extension what all values it will add?

3. Earlier we have using visitorID but planning to have ECID with this upgrade, What may be the disadvantages of using this extn. as it will impact the visitor count. So eager to know the best practices on it. 

4. We have multi suite tagging and along with the Global repost suite we have iOS and Android specific report suite. If we use a single mobile property in Adobe Launch how the report suites can be parametrized as per environment.

5. What are the best way to create and manage processing rules since this might be a big deal to create and manage many processing rules.

6.What will be the perfect way to populate the product string?

Thanks in advance!