If you want to walk off the bike in your cycling shoes for any meaningful distance comfortably you should buy mountain shoes/pedals over road. Road pedals/shoes can be a little lighter (no tread on shoe) and there's a little more surface area between the cleat and the shoe to distribute forces, and they often align the foot a little more specifically, but they're terrible to walk around in as the cleat is not recessed.
MTB pedals offer very good performance (many recreational road cyclists ride these also) but allow you to walk off the bike. Depending on the exact cleat/shoe combination the cleat may impact your walking some, not impact your walking much but make some scraping noises, or not interfere with your walking at all. For what it's worth crank brothers cleats are a bit lower profile than SPD. I've used both eggbeaters and SPDs, and frankly they're both fine (the eggbeaters do clear mud better for cyclocross/mtb but that's probably not a big concern for you). SPDs are more common and can be bought cheaper, Eggbeaters are lighter, have more entry points, and have lower profile cleats. I think they may be slightly easier to get out of. Take your pick. More money generally buys you lighter weight, but reliability and functionality of inexpensive brand name pedals are good. I don't know about offbrand stuff, probably a mixed bag with some good performers thrown in.
Shoes range from ultra-stiff carbon soled MTB shoes that are really nearly identical to road shoes with added lugs for walking and 2 bolt cleat compatibility, to much less stiff shoes that are almost like sneakers. You can walk around in a really stiff shoe some, but I wouldn't want to do it very long, whereas I've spent hours walking and standing in more flexible shoes. For what it's worth, I really like my Specialized MTB Sport shoes. They're entry level performance oriented shoes, so they're reasonably stiff while still being comfortable to walk and stand in, are actually very light, and the velcro makes them easy to take on and off (to change into normal-person-shoes.) I also really love my stupid expensive S-Works MTB shoes for my recreational riding, and they'd be totally fine commuting as long as you're not doing any more walking than, say, some grocery shopping.
I've had the SPDs with flats on the other side. They work fine, but I found I used the flats uncommonly, and they reduce pedaling clearance around corners (a fact I became more aware of after clipping a pedal turning on my touring bike, after having mostly ridden my cyclocross bike). They're heavy and more expensive. Still, if you think you'll use the flats, they're a reasonable call.