E2EE meaning survey questions and answers are encrypted locally & decrypted locally. The server or any other actors can't view survey questions aside from users its shared with and survey answers are only readable by the owner of such survey.
This means on a data leak, nothing is readable.
Yea Purplix.io is still in development, so it isn't live yet. Hense the fail DNS lookup you show.
Don't know the complete inner workings of Cryptpad. But it appears Purplix uses more modern encryption, uses more modern frameworks & has more safe guards against MITM attacks. Also additional options like captcha, proxy block, account required etc.
No, survey questions and answers are encrypted & decrypted locally. At no point does the server or any other actors can view that plain data said from whom the survey is intended for.
I understand encrypted-at-rest to mean that the data is always stored under encryption, except when it is being actively being used or displayed. Am I wrong?
So in your usecase also, all data is stored under encryption and only decrypted by the surveyor or the surveyed; so this is encrypted at rest, no?