Weak sense stationarity sufficient for multitaper spectrum analysis? This is a general question on multitaper spectral analysis of signals and stationarity

I work with time series which are non stationary. In this regard I have two questions


Is weak sense stationarity of second order sufficient to apply multitaper spectrum to compute valid estimates from contiguous time series objects or strick sense stationarity is required. 
Multitaper works with signals that are periodic, quasi periodic, nearly periodic, and semi periodic signals however I find hard to diferenciate between periodic and the rest as to be able to see if the series I am working with belong to any of the mentioned groups.  


Your help will be welcomed
The answers to the questions are 


Yes WSS is sufficient. 

Quasiperiodic 





Semiperiodic