Master no louder than -9 LUFS short-term at the loudest moments
(with True Peaks no higher than -1)
That's what Ian Shepherd says at least.
SimulAnalog guitar suite has a pretty decent Univibe free VST plugin.
I test an Aurycle kit microphone (a u47 clone, all stock), the Austin ribbon kit (with Cinemag transformer), a Rode NT1-A, and an AKG C12...