I have previously tested 'new' Outlook, and reverted to the older version again for multiple reasons, this thread being just one of them.
Unfortunately, the company IT team had to remove Office entirely and reinstall in order to fix a recurring bug, and I now have no ability revert to the older version.
As a warning however, not only is the delay email sending function not available in 'new' Outlook, it simply deletes the rule(s) using it and doesn't give any indication that it has done so.
So you can end up thinking it's still in place, and working, until after the point where you 'needed it in place'; not something I've directly experienced thankfully, but still sub-optimal to say the least.