If I join a team, can everyone on the team see my existing personal boards?

[J M]

I use Trello with several personal boards, that I want to keep entirely private. If I join a team, can everyone see them? Would it be smarter to start a new Trello account for each team I join similar to how each Slack team has its own login and they are completely separate? I noticed there is "add an account" functionality now with Trello so thinking that might be smarter. However, I wonder if I can copy cards between different accounts too? Many questions, this Trello teams implementation is very confusing and unclear.

[milynnus]

@J M 

Being confused is perfectly normal when you are new to Trello. We went through that phase. 
Only members in a private board can edit a board. Team membership should not affect that. 
You can copy cards across boards for boards where you are a member. That destination board could have another person as the admin and ‘own’ that board. 
If you need help do let me know. 

[J M]

So people on the team can never see my board, even if I take a card from the team and put it on my board? How easy is it to mess this up and inadvertently give someone access? Will my idea about a completely separate Trello account solve this issue or make things more difficult? I don't understand why they didn't just make this work the same way as being in different workspaces in Slack where everything is completely insulated. 

[milynnus]

@J M 

As admin you have full control of private boards. If team membership does not overlap, you should be able to mitigate that concern. I do not enough about Slack aside from some development work done recently.  

My greater concern as developer is how easy it for list and board names to be changed in Trelllo. It can mess up the automation.