Probably a good idea to define "efficiency". IMO a firm connection to the pedals does not make you more efficient. It simply allows you to go a bit faster when going as fast as possible is critical. If you regularly contest field sprints and mountaintop finishes while touring, then you will want clipless. Otherwise, a truly firm connection to your pedals is relatively unimportant.

So with that in mind...

Toe clips and straps are as "efficient" as anything if you use proper shoes and good quality straps and set them up perfectly. But that is all but a lost art these days, and even if you do manage to get it right, they will actually be more difficult than clipless in use, because you will have to reach down and undo the strap each time you come to a stop.

Another way to do it (and one that I prefer) is to use clips and straps with rubber-soled touring shoes. This is comfortable and easy to get in and out of, but is not nearly as "efficient" as either clips and straps with cleat, or clipless. Clips and straps with tennis shoes or what have you generally does not work very well, because the soft soles allow the pedal cages to dig into your feet, which can become pretty unpleasant after a while.

And though I am a die-hard fan of clips and straps in general, it's hard to find any area where they really work as well as clipless. I am kind of shocked to hear all the stories of cyclists toppling over because of clipless. They really are not hard to learn. And shoes for clipless are widely available, including many styles that are perfectly "walkable" and don't make you look like some kind of alien or haute couture reject.

Short version? Big soft platform pedals with no clips and straps work fine for many tourists, using whatever shoes you like. Clips and straps with "standard" road pedals also work fine, but you'll want bicycle touring shoes to go with them, which are pretty hard to find these days. Clips and straps with stiff, cleated shoes are great on the bike but very hard to set up properly and very awkward when off the bike. Modern clipless works great and gives you all kinds of options, and the "risk" is vastly overstated.