Can users of Paratext 7 and 8 share via Send/Receive?

No. Due to the changes in the new version, data can’t be shared back to Paratext 7.x via Send/Receive. This is the reason for a new Paratext 8 data directory and send/receive server. As a team, you must coordinate the migration of your data to Paratext 8 together. You can run Paratext 7 alongside of Paratext 8 as needed to access projects that have not yet been migrated. Paratext 8 will only be able to open Paratext 7 projects after completing the migration process. At that point it is advised to remove the project from Paratext 7 to prevent users from accidentally editing the data in 7.