This sounds like group messaging might be more appropriate for you, i.e. applications are made by sending a message to a group rather than creating a topic in a category and only members of that group (plus the sender) can see the messages.
Unfortunately form templates aren’t available for group messaging. I think I asked about this in the context of support enquiries, someone did, but I don’t know whether or not that’s something intended for the future.
This has been discussed in other topics, e.g. #4 (and subsequent replies) in Offering "private support" as part of a public support community, where my impression has been that they don’t want to do it as it would add a lot of complexity to category permissions for something which is already there with group messaging.
It’s also more flexible with group messaging because participants can be added/removed as appropriate. E.g. if recruiting for a technical role, you might have applications go to an HR group and once they’ve done sanity checks on the application, they could add the relevant technical group as a participant.
I would definitely like to see form templates extended into group messaging eventually for scenarios like these.