I'm in the process of setting up SugarCRM for my organisation and I would like feedback from someone with on-hands experience:

We're going to load leads into Sugar. They will be used by salesteam to call new clients.
Leads will be converted to Accounts, Contacts and Opportunities.

What is best: To relate calls/mails to? Accounts, Leads or Contacts?

We expect to have
Between 1 and 3 contacts connected to each account.
About one new opportunity connected to each account each month.

When converting a Lead using Sugars default installation, mails/calls relates to the contact, but with our usage, it seems better to connect it to the account.

It's important that our salesperson #1 can easy read our salesperson #2's activities on a specific account.

Would it make sense to relate a call/mail to both a Contact and an Opportunity?
Or can I define the default view of my Account to show "activities related to Contacts related to Account"?