I haven't used either of these features but I'm thinking about shooting some things with an external audio recorder, so I'm wondering about the pros and cons. Is the Syncing/Merging feature of PP good enough to eliminate the need for timecode? Will it work for three cameras and two externally recorded audio tracks (a boom mic and wireless lav recording the same thing, plus bult-in camera mics)? Thanks for any tips.
Most of us don't recommend the "merge clips" process much, as it has a number of limitations. The "multicam" process is far easier to use, fewer limitations. It still takes a bit of working with to understand why it does this one time, that another. But not bad in all.
You can take a bin of clips, select all, right-click/Create Multicam ... and it pops up a dialog. One option is to join by audio, and that tells Premiere to look for either a separate audio file that matches the audio in the clips, and use that as the base for the match ... or if there's only camera audio, to use the camera audio.
You can actually have say five interviews, each with one video clip and one separate audio, in a bin. Select all, create multicam, and Premiere will give you five different 'multicam clips' matching each video and its accompanying audio.
It's a pretty slick process as you get used to it.
I wouldn't take it off your wish-list yet! Real jam-synced time-code is simply a marvelous tool to have in the toolkit.
But ... multicam can do a lot to get you going. Where the jam-sync blessing comes in is over long-recordings, say above 30 minutes, and especially where the cameras may auto-break the files into smaller bits. Or where some cameras are simply not 'on' during the full recording.
And jam-syncing is a massive boost for reality shows. It can get you to a time-correct timeline much faster.