A few points...

It has been pointed out that clips/straps with proper cleats offer at least as much retention as the best clipless set-ups. And yes, people do still use cleats -- head down to the local velodrome and watch the sprinters at work.

I'm not sure that there is any point in discussing "best clips and straps" if they are going to be used with tennis shoes. No clips and straps will retain the shoe/foot at all well without cleats.

Beyond that, I will note that the trend for clips "designed" for doubles is foolish. Assuming a traditional clip with one loop holding a single toe strap, placing an additional toe strap ahead of the first one results in very little additional security: your toes aren't really contributing to the pedal stroke. The place to put a second strap is behind the first one, behind the ball of the foot. This is best accomplished by threading the second strap through the rear pedal cage plate and then attaching the top of the strap to the front one so that it doesn't flop around. There are fancy leather do-dads that perform the function but electrical tape works just as well. A pedal so set up will offer unbeatable retention with proper cleats -- even crashing won't often pop you out -- and probably offers the best (still inadequate) retention with tennis shoes.

It's also worth noting that the great majority of toe straps currently on the market are trash for most purposes. That includes all straps made out of a single piece of leather or nylon. These stretch under force -- even if you get them as tight as you can by hand they will still allow your foot to come out with little effort. Laminated straps are the only straps that can truly offer retention -- and most of the currently available laminated straps are no good. I've seen them delaminate after a few uses, I've seen buckles that don't grip well and buckle rivets that snap, and I've seen leather so soft that the serrations of the buckle tear right through it. I am sure that there are several good ones available, but the only ones I know for a fact to be world class are from Toshi.

Toe clips? Plastic sucks. Aluminum works fine until it breaks (it will). The steel ones are mostly all the same, but Campagnolo clips seem to have heavier chroming and don't rust as quickly as Christophe and MKS.