How problematic is it going to be going from 7.2.1 to 7.4.3? We’ve done a moderate amount of customization so I would be very surprised that is could be achieved without running into some issues. What would be best practices to insure the smoothest upgrade?
It really depends on how yoiu have done your customisations.
If you have customised via Studio or Module Builder and then uploaded the new modules you shouldn’t have any problems updating.
Always take a back up of both the files and folders as well as the database.
If, on the other hand you have customised things programmatically you will have to check if your files are being over written.
This may not be very simple, depending on the amount of files you have created and whether you have edited existing files or created new custom files.
Additionnally, you may have copied original files to the custom folder and then edited these copies. You will have to check whether these files are being replaced with the upgrade and, in case they are because they have been modified, you will have to re-edit them with your changes or just add the new modifications to your custom version.
As you will see it may be a trivial task or a complex task. It really depends on the situation.
Have you ever update ? What exactly is the problem…
Normally everything works, if the personalization were done correctly.
…to be safe, dupilcate your installation in test environnement, and try and check