Yes, admins can limit other users' access and permissions very specifically. For example, if you have a user who manages tenant inquiries, but you don't want them to be able to access your Owner lead pipeline, you can give them access to the tenants pipeline and not to the owners.
Also, you can restrict their permissions within each pipeline or process type that they have access to. (I can keep Charlie Brown from seeing leads assigned to others or unassigned leads, or allow him to export leads, or allow him to manage the email/text templates, but not the stages & workflows.)
You can update the permissions for your users by clicking Settings > Users in the lefthand sidebar in LeadSimple and then selecting the pipelines and processes you want them to have access to on the right side of the page.