Hi,
I am a bit confused because I have seen so many different variable name conventions. How should I construct my variable names if it should be as OPC UA compliant as possible?

There isn't really an idea in naming your variables to suit up with the OPC-UA driver, as it uses the runtime name as a large part of the total string.

I replaced all of our tagname conventions with a single * to short it down, but we use CCS code for tagnames as its a much more wholesome naming strategy than just using TT, PT, etc. It is the IEC 81346-2:2019 standard and you can check out the latest CCS(2014) standard as its called CCI(2020) now here, its in Danish, but can give you an idea in the examples: https://anvisninger.molio.dk/aftale_og_kommunikation/eksempelsamling_installationer_cci_2020/eksempelsamling_installationer_a650/l1%20automationssystem

We use it in a way like this L01 for automation in building 1, LC01 for automationsystem 1 in, BTA001 for temperature transmitter 1, so that component is called L01.LC01.BTA001 and the beautiful thing is, that a temperature transmitter in a cooling plant in building 6 is called H06.HC01.BTA001 so components are always using the same codes and there is codes for many different systems. No more remembering which plant TT50143 or TT50144 was used in :)

Here is a example from one of my projects
ns=4;s=|var|CODESYS Control for Raspberry Pi MC SL..oCMD_CONTROL.xCMD_MAN
ns=4;s=|var|CODESYS Control for Raspberry Pi MC SL..oMANUAL.bDECIMALS
ns=4;s=|var|CODESYS Control for Raspberry Pi MC SL..oMANUAL.iVALUE_TYPE
ns=4;s=|var|CODESYS Control for Raspberry Pi MC SL..oMANUAL.rVALUE

As you can see, the string has this long runtime name, that you can not change, in front of it all, but good practise is to use pre-fixes for datatypes as seen above.

A little more explanation about the IEC standard here http://81346.com/english/about-81346/about-81346-2-2019-edition/

Thank you both, that´s helpful!