I did pick the DBrand Kill Switch case (including. skin and screen protector) for both me and my partner. It was on the pricer side, but I'm pretty happy with it. Feels quite good to hold and certainly rugged enough to protect it. The skins also stop us from getting each others decks mixed up.
As for a dock, I picked up the Anker one and it's alright. Would have preferred the official one, but everywhere was charging a hefty price for importing it.
I already had a hefty battery pack for travelling. Haven't needed it much myself, but my partner recently made good use of it for an international flight.
They do have e2e for emails. Any emails between Proton Mail users are always e2e encrypted, as are any emails others send you which they've encrypted with their own maio client. If someone sends you an email unecrypted (most email is), then Proton will encrypt it for you and put it in your inbox. They can't read it after that, but there is some trust required that they don't store/look at the unecrypted email before then.