Garmin 800 is the best thing I bought for the bike. Screen is small though. It has been fine for walking and riding in areas I was unfamiliar with.
There are probably walking garmins with bigger screens for less money.
You get an is map with an arrow and a line to follow if you load a route. It makes navigation much quicker.
You can load your own maps. I’ve put some on there for an upcoming ride to Italy. Official ordnance survey maps are v. Expensive but you can buy the whole UK map bundled with the device which is well worth it.
I find the garmin software for my PC poor so I create routes online. You just click and join up the dots on a map on your PC. Drag the file to the device and away you go.