Yes and no. If you want to use TNS names, then yes, Oracle needs to be able to find it, but I think so long as the path to the client is in the Path variable that would work. Using TNSNames is more a full client than an instant client approach, though.
With just the 32 bit client, you can connect by:
myuser/mypassword@localhost:1521/xe
If you want to use TNSnames you could shorten that to
myuser/mypassword@XE (where XE is the TNS name set up in TNSnames.ora)
From the point of view of the clarion connection only the TNSnames.ora is of any interest (and you can do without it). Listener.ora is a server file, not a client file. sqlnet.ora may be required in some special cases, but is not a file you would normally need or modify.