I had to fill out the 125-page SF86, not SF85P. I was under the impression that all new hires as of 2017, at least, have to do the SF86 regardless of terminal/en route track.Its just the term used. The "conditional" part is actually a waiver if preliminary checks have no red flags, allowing someone to start before the entire process is complete. You don't ever get an actual security clearance (S, TS). Risk and Sensitivity are the criteria for clearance/BI requirement. ATC is moderate/non-sensitive. The SF85P is whats used, and the BI is T2. NACI is a background check standard, not a clearance level. It's the lowest (T1). One step above is the moderate background investigation (T2). Once fully "cleared", the only thing on record is a positive T2 adjudication from the FAA. The agency is one who decides to give a positive/negative adjudication.
This site has a ton of info about security clearance stuff: Position Designation and the Type of Investigation Required - ClearanceJobs