Protonmail is a fully encrypted email solution based in Switzerland. It uses PGP encryption (see below) and is recommended by specialists worldwide. Protonmail offers a limited free option for low volume users, but the full solution costs 4€ per month. It is currently banned in Russia, but still accessible via Tor & VPN services. Both sides require the usage of Protonmail for PGP to be enabled in the conversation.
PGP (Pretty Good Privacy) is an asymetric encryption system. Your private key allows you to decrypt contents, and your public key is given to your correspondents so they encrypt their contents in a way that only you will be able to open. Protonmail integrates it seamlessly, but there are also options for you to use it on its own. This requires an e-mail client such as Mozilla Thunderbird along with a non-web-based email service, and obviously a bit more work.
The following applications are recommended by privacy specialists:
Signal is the reference messaging app for privacy-conscious users. It is based on the Signal protocol. It is free and recommended by the EFF and hacktivists worldwide. Its main issue however is that your contacts may not be using it (yet). It includes 1-on-1 video calls.
Threema is a solution developed in Switzerland and used within the Swiss armed forces. It is not free (a single purchase of $3.99 is necessary), and obviously much less popular than Whatsapp, Telegram, or even Signal.
The following applications are not recommended if privacy is your main concern:
Telegram is not end-to-end encrypted, but its advantage over Signal is that you can register an account without registering a phone number. It is also free and more widely used than Signal, which could make its adoption easier (your contacts might already have it on their phone). It now allows video calls.
Whatsapp is owned by Facebook. It has officially adopted the Signal end-to-end encryption protocol, but its implementation cannot be verified since no external privacy assessment are taking place. It also privileges ease of use over actual security (using cloud backups for your conversations for example) and should not be considered safe. It is free and allows video calls.
None of the usual software (Zoom, Webex, Skype and Google Meet) are considered secure for group video communication. End-to-end encrypted group video conference solutions include the following:
Jitsi supports encryption in various manners. It is also available on the App Store and Google Play as well as Chromium browsers.
FaceTime is great for up to 32 participants, but only available for Apple product users (MacOSX & iPhone/iPad).
Whatsapp works for up to 8 participants, but only allows video conferencing on smartphones.
If you require secured messaging and storage, backing them up automatically in the cloud as suggested by Whatsapp is a bad idea. There is no point in using end-to-end encryption if you end up storing your data insecurely after the fact. As usual, this is a tradeoff between security and safety (prevention of loss).