The thing that has always stopped me from using Notion is that it's not end-to-end encrypted. So much personal data will be uploaded, with the possibility of abuse and/or getting stolen in a leak, or as often happens, some other company buying them including all your data, and changing the policies;

For tasks i've been using OmniFocus, which is an excellent app. e2e + syncs between all devices.

Haven't found a good Calendar app yet of the same quality...