Here is fine.
so, I have used all of the above mentioned protocols (for years) and in my experience, in node-red (and general IoT), MQTT is simply the best medium. OPCUA is a BEAST (read the spec if you have a spare year). Its complex and heavy. dont get me wrong, OPCUA is a tremendous and detailed specification but if you want to get a simple value from A to b and you have MQTT at your disposal - chose that. every time!.
As for modbus - the nodes avaiable for node-red work for the most - but a quick search of this forum will reveal how much people A struggle with it and B how it can crash node-red (not good!)
Are you familiar with MQTT?
If not - read this
In fact, give it ago - it will take you 5 minutes.
Lastly...
I would strongly urge you to watch this playlist: Node-RED Essentials. It is by the developers of node-red. They're nice & short and to the point. You will understand a whole lot more in less than an hour. A small investment for a lot of gain.
