on flare fittings i still use anti seize w/o issue. no fun removing rusty flare or replacing damaged brake line.
i tighten flare nut pretty firm; tighten more if required to stop leak. even brand new double flares can leak until firmly seated.
never found good data for flare nut or pipe thread torque limits so i pretty much rely on calibrated elbow. i have tried counting turn method but don't have data for all sizes and materials.
i've had bare brass pipe threads leak. i normally use ptfe tape on brass pipe threads and never had issue.
i use ptfe tape or pipe dope or both on pipe threads.