Is it possible to restore individual app data (over iCloud)?
This is reasonably possible with a little configuration work on your old iPod Touch. The key will be to turn off everything except what you want on your new iPhone. Also, there is some possibility that miscellaneous settings and such will sync over. However, we should have control of basically everything.

Another important note is that the restore cannot be done after you set it up as a new device without re-wiping the device. iCloud, unfortunately, doesn't allow selective restore, but it does allow selective backup. 

What you will need to do is open your Settings app on your iPod Touch and select "iCloud". Go down through that first list and disable everything there. I'd probably leave "Photostream", "Documents and Data", as well as "Find my iPhone" enabled. If you would like "Contacts", "Calendars" and such synced over, go ahead and leave those switches on as well.

Next go down and select "Storage and Backup" > "Manage Storage". Leave all the Documents and Data enabled there - those will only be referenced/downloaded if you have the applicable app. But, if you desired, you could disable some of these as well.

Now select your iPod above "Documents and Data" and start working through the list. Turn off everything you don't want, and leave on anything you want. This could take several minutes as you will have to choose to delete all the unneeded data.

If you happen to turn off a switch accidentally that you want left on, turn it back on and perform a manual backup. That should re-send the data to iCloud. 

Again, while this may happen to sync things that you didn't really want restored - like settings - I can't think of anything that would do that. Either way, this is the control we have. 

After all the above is complete, wipe the iPhone 5, restore it from your iPod Touch backup, and configure your iPhone 5 to backup. You can now go through and re-enable everything on your iPod Touch as it will be listed as a different backup and will no longer affect your iPhone's current data situation.

And, of course, congratulations on your new iPhone