Dear @Lemons, Kathryn,
Thank you for reaching out to the Microsoft Q&A forum. I am happy to assist you.
In Teams, a standard channel is visible and accessible to all team members. Standard channels are designed for collaboration and communication across the entire team, so it’s not possible to restrict access for a specific user if they are already a member of the team.
For more information, please refer to: Overview of standard channels in Microsoft Teams
Besides that, you can also consider using a private channel, which allows only specific people in the team to have access. This can help you restrict certain users from seeing channel content while still keeping them in the team. Visit here to learn more: IT Admins - Private channels in Microsoft Teams
As a workaround, you may also turn on channel moderation to help manage member activity within the channel.
Go to Teams > Click the three dots icon next to the channel > Manage channel
Click to the drop down under Channel moderation > On
Then you can choose moderators to manage member activity within the channel.
Regarding the content inside the channel, you can export data by using the Teams Data Export tool.
For information on how to use it and the requirements, please see: Export options for switching from Microsoft Teams
Lastly, here is how to remove the Notes tab from the channel:
Go to the channel > right‑click the Notes tab > Remove
Click Remove to confirm the removal
Then the tab will be permanently removed from the channel
I hope this information is helpful. If you need any further assistance, please feel free to reach out. I am here to help. Thank you very much for your understanding and cooperation.