Power Spectrum Analysis
Hopefully you understand why and in what situations those methods are used. 

The integer 'K' in the Bartlett and Welch methods is not arbitrary.  The value of 'K' is a "trade off" that you must make. In both methods, the greater is 'K" the lower is the variance in your final DFT results. That's a good thing. What the PSD's author doesn't tell you, though, is that the greater is 'K" the larger is your final DFT result's frequency-domain sample-to-sample spacing (measured in Hz). And that's usually a bad thing. So you must decide what value of 'K' is acceptable to you. I'm not qualified to comment on the Blackman-Tukey method.