Heads up - Pedal shape is probably more important than shoes. If you’re a forefoot peddler (likely if you use clip in pedals), concave pedals are a huge upgrade over flat flat pedals. Mid-foot, you might like convex. The shape helps you locate the pedal. The shape also works against stiff shoes soles. One advantage of cycling specific shoes is that they have a smaller tread features to work with pedal spikes patterns (running shoes would be the worst shoe here). Cycling shoes also have better foot protection if you’re hitting a trail - I wouldn’t even go onto a mellow trail with the occasional rock/tree with Vans.
In my experience, there’s a decision whether to go flex sole or stiff sole. Stiff soles is probably going to work better if you’re used to cleats and use your forefoot for pedaling. Soft if you’re going to use your mid-foot. Semi-stiff in the midfoot of the shoe results in your feet being TORTURED (some Giro urban shoes i tried) . If one goes stiff, you’re really got to deal with the shape of the shoe/insole just like stiff road/mtb shoes. Basically, all flat pedal shoes are going to be FLAT inside. I bought some FiveTen Trailcross, which are stiff. I spent quite a bit of time getting insoles to work with the gym shoe top.
If someone is going around your neighborhood, I’d try a Vans and the right pedal. If you’re going to be pedaling for hours, you’re going to have kiss some pedal/shoe frogs. If you’re descending, you can probably figure it out pretty quickly.
Shout out to Shimano T8000 pedals if you dipping your toe. I have have an ‘around the hood’ and occasional trail MTB. These work perfect. If you get the wrong side, you can still pedal your slick carbon sole xc shoe on the flat side. They always seems to be on the correct side though. The concave flat shape is way better than the flat flat EH500. The platform takes the trail hits like the proper xt trail pedal at the same weight Shimano PD-T8000 Dual Platform SPD Pedals | Explorer | Ride Shimano