It is logical to assume that the very last maintenance release of a version will be the most stable to install and use, e.g for NR v1, it is NR v1.3.x and NR v2 is NRv2.3.x? Can you select a particular version with the generic install script (for Pi install)?
That chart shows the planned release schedule stretching into the future. At the current time, there is no 2.x version of Node-RED. It's being worked on and we should have a beta release very soon.
We would always recommend installing the latest stable version of Node-RED. The 1.x stream will soon enter maintenance mode and only receive critical fixes. The overlap is to give people plenty of time to upgrade to the new major version taking into account any breaking changes that may have occurred.
We haven't yet decided on what the Pi install script will do. It will certainly default to the lasted stable release. It could have an option to install the current maintenance release.
Just to amplify
the current install script will leave alone an existing nodejs 10, 12, 14 (or greater) install,
If it does install nodejs it will try to install latest node 12.
When we move to Node-RED V2 the script will (by default)
leave alone Nodejs v12, 14 (or greater)
Otherwise will try to install nodejs 14 - but may have an option to force node 12 (or 14) - as we have seen some nodes with binary (eg Modbus and SQLite) - being problematic to upgrade so we want users to be able to stay on 12 for a clean install if they so wish.
The latest 1.3.4 core install is perfectly happy with node14.