Can't add any more that what has been written up but I certainly can relate to you and the photographs.
I'm NW3 with thinning and at present wearing two partial pieces. Although I'm still trying to establish a bond that I'm happy with, the actual wearing is fantastic and feel a lot better.
Started balding at about 20, it's been a slow process, bit by bit and now at 28, I decided to try this route and although I'm sure there will be downs along the way, the ride has been great and I feel so much happier with my old hairline and like a few have said I instantly look a lot younger than the grown out horseshoe.

For me it's about feeling the best you can and feel happy the way you look. I know a few guys who are in worse shape with their hair and they seem happy enough but we are all different and if it's getting you down, you should at least give this a go. If it doesn't work out, you can go back to concealers or the shaved route.

Like you I was caking the concealer on and it was beginning to look too obvious probably and also it was such a pain and worry. If someone touched your hair, if you popped your head up against a pillow, even going into certain places where the lighting was bright and people would notice something up and it's expensive too. Not going to rip into them as they helped me a lot but for me, they are ideal for a small thinning area and not if you are thinning all over or receding.

As for the transition period. - There are plenty of options to avoid being busted. You could even grow out your hair at the moment to a medium length option still using your concealers and then once you get the cut-in and the piece, you could cut it to a shorter style and I'd bet that everyone would just say 'nice hair cut'. You could also try growing in some facial stubble for a few weeks/months and then shave it off when you get your hair, again, I think most folk would notice the beard disappearing rather than the different hair.
You can order a thinner density, before slowing building up with the next order to a style/density you like.
You can also continue with the hats and caps and then gradually go out with the hair step by step.

All the best.