Good morning,
My number 1 requirement is to be able to comfortably walk in them possibly up to 10-15 miles!
I once walked about 8 miles in MTB shoes and not only did it destroy them, they become very difficult to walk in after about 5 miles. The steel plate that the cleats bolt into became detached and started to stick out of the side of the shoe, catching the opposite ankle every step unless I was careful.
I am no guru on shoe design but it does seem likely that there is going to be a massive design conflict between a design that can takes the loads imposed by the two small bolts of SPD when pulling up on the pedal and the pressure imposed by the SPD contact area when pushing down and one that can flex enough for comfortable walking.
The general consensus amongst experienced cyclists is thats the way to go.
I know that you haven't asked about going clipless but; many
experienced cyclists don't like/use clipless, if you read cycling mags or talk to wannabe racers then you will get the impression that clipless is essential. Most of those who don't use clipless simply don't say anything as what's the need to or the point of?
I tried SPD for 2 months, 18 miles each way 5 days a week and could not get on with them, two "clipless moments".
... and this is from someone who grew up using toe clips and straps and shoes with shoe plates (you may need to look that up
https://www.thomsonbiketours.com/blog/2020/12/03/evolution-of-cycling-shoes/)
Although "clipless moments" are often joked about, they can be life changing as well, if I fall over at 1mph into the path of a truck the fall won't hurt and even if does it will only be for a few seconds! Squash!
I may have to delay purchase until i have the wonga
It's not clear to me if you already have clipless pedals or will have to buy those as well, if buying you might want to consider something like this. One side takes SPD cleats the other is a flat platform, this allows a lot of flexibility in clipping in or not.
View attachment 706677
They will also be useable if you decide that clipless isn't for you.
Good luck.
Bye
Ian