Yes, you can!
If you want to copy from one project and paste in another project, simply use the standard shortcuts for copy-paste.
Copy - 'Cmd' or 'Ctrl' + 'C'
Paste - 'Cmd' or 'Ctrl' + 'V'
Alternatively, you can also right-click while selecting the component or screen in the source project and choosing 'Copy,' and then choosing 'Paste' among your right-click options in your destination project.
Your pasted components or screens will always appear in the theme of the destination project.