There are cleat types and there are cleat mounting pattern types. Some mounting patterns have been popularised by cleat types. The most popular cleat types for road shoes is Look three-hole triangular pattern. Some road shoes also accept the Time four-hole pattern and/or the Shimano SPD two-hole pattern. Some road shoes will accept all three. Most MTB shoes only accept the Shimano SPD two-hole pattern.

As far as cleat types go, most road cleats that use three-hole or four-hole patterns are not very walkable. Then again most road shoes are not comfortable to walk in to begin with and have a very limited amount of actual tread. In contrast, MTB shoes are designed for walking/hiking. There are also other types of "cross" and recreational cycling shoes which are quite walkable and generally accept multiple mounting patterns.

As far as pedal systems go, do a search on here for keywords like "speedplay", "spd", "atac", "bebop" and "look pedal" and you should get a good smattering of prior relevant posts which will highlight people's opinions of various systems.