If I add a second bank account can I combine and separate reports as needed or will the other account be entirely separate?

Happy Friday, @mam8008. 

I hope your weekend is off to a good start. I'm here to give you some insight into if you can combine or separate reports by each bank account. In QuickBooks Self-Employed, all of the information that pertains to a report will be shown. Example: A profit and loss report will show you all of the transactions that are recorded in the Transaction Tab. If you do connect another bank account, it will combine those details from both accounts into the report. At this time, there isn't a way to customize or separate the reports by a bank account. 

Here's an article that may come in handy: Connect bank and credit card accounts to QuickBooks Self-Employed.

If you have any other questions or concerns, don't hesitate to ask. Enjoy the rest of your weekend!