ロードバイク ペダル & クリート

For most riders, yes, having a solid but safe connection between them and the pedal helps efficiency and ensures that feet don't rotate or slip off pedals. However, there are lots of mountain bike riders who prefer to use flat pedals with flat MTB shoes. Also, for very short (5 minute or less) trips to the shops, pub or office, it might be easier to use regular shoes - dress for the location, not the trip.

Many riders find double sided pedals, such as Speedplay and lots of MTB pedals are easier to get clicked into quicker. However, single sided pedals tend to be weighted so the cleat slips in relatively easily too. So, wiith a little bit of practice, it is relatively easy to click in to all clipless pedals quickly.

With many pedal systems it is possible to reduce the spring tension, this makes it easier to click in and click out - this often helps riders when they are new to click in pedals.

There are no hard and fast rule with this. Generally, the worse the conditions you regularly ride in, the more MTB type pedals and shoes will suit - particularly if your rides include touching shoes down on the ground a lot, or walking / pushing. The more smooth, dry, fully ride-able and predictable your usual gravel tracks are, the more likely you can get away with road pedals and shoes.

Yes, MTB pedals and shoes are ideal if you walk as well as ride your road bike. MTB shoes have recessed cleats which makes them much easier to walk on.