Form templates are stored as files within your teams SharePoint site. This means that you can control access to specific forms using SharePoint file permissions. This also means you can use SharePoint's inbuilt "Check Permissions" feature to audit weather a user has access to a specific form using the steps below.
Locate the source file for the specific form in question. This should in the following document library location
โTeam Forms > Form Config > Form Name > form.published.json
Click the "..." icon next to the form.published.json file then click "Manage access"
Within the access management popup click the "..." icon in the top right-hand corner followed by "Advanced settings"
This is open SharePoint's permissions screen. Click "Check Permissions" and enter the user's email. Any of the permissions shown below will mean the user has access to the form and it will appear for them in Team Forms:
Read
Edit
Owner