>so I do wonder if it's missing any new state of the art / best practises.

https://nostarch.com/serious-cryptography-2nd-edition should have the latest info, it's approachable and goes into pitfalls. https://www.manning.com/books/real-world-cryptography is another.

>As a software dev, I have all these boxes I could use, that come with so many caveats "if you do this, but don't do this, no do that, don't do that"... It's very tricky trying to work out how to glue the pieces together without already being in the field of crypto

Until you know more, strongly consider suggesting the company just hires someone who knows that. Just because you're available to do it, doesn't mean you should just yet.