Generally yes, then you can automatically get updates if a new version is released with bug fixes. The exception is if you want the very latest version of an app (or a later version than is in the repository). In particular if an app is developing rapidly so the version in the repo does not keep up. Such an exception is node-red itself, which is why it is generally recommended to use the script in the node red docs.
There is no need, if you are happy with what you have installed.
OK, I've had this setup running for a day now, in two separate networks (each with an R-Pi 4). Scheduled to run four times a day, at 13 minutes after the hour.
So far, only once got a returncode 1 from speedtest-cli, no idea what that means.
All other seven measurements were OK...
Don't know, I did not have a debug node attached when this happened.
But after running for almost two days, I am happy with this setup. I will get 4 or 6 measurements per day, and have put together some code to compress the measurements down to a single value per day. So my graphs will not show annoying gaps, or multiple vaues....
I'll leave it like it is.
The only nagging thing is the fact that I'll never know what was wrong!