Is there a particular process to update plugins, or we just install the new releases on top of the current installation?
Yup, just install new releases over the top.
How can I subscribe to get notifications for new releases?
We only send newsletters for stable releases, which you can subscribe to in your profile here at Joomlapolis. New releases will also show in your Joomla backend in your control panel as we configure a module on first install to show new releases. You can also check CB > Plugin Management > Install New Plugin > Install From Web as it has a built in update checker and an Update All button. Additionally CB > Plugin Management has a version column that'll let you know if a new release is available (version will be colored red).