On Oracle 21c XE, what should ORACLE_HOME and TNS_ADMIN be set to?

In my Windows Oracle 21c XE installation I have the product installed under: C:\Oracle\product\21c Below that there is: dbhomeXE which contains the bin directory and also network. However, I also have: C:\Oracle\product\21c\homes\OraDB21Home1 This also has network/admin. It looks like dbhomeXE should be the Oracle home, but I have seen it also mentioned that it should be the directory above. I assume TNS_ADMIN should be $ORACLE_HOME/network/admin? But how does it matter anyway? What uses ORACLE_HOME? It isn't currently set on my system and sqlplus launches, although it can't find the PDB I have created. **EDIT:** The variables are used in a batch script to run sqlplus, so I am talking about the client side really, although both the server and the client are on the same PC.