Is it necessary to use a whole variety of meditation techniques?
I found experimentation helpful before I realised that some meditations require some form of mental application or you could refer to it as volitional noise. This, as I learned, became averse to me and so my practice is meditating while 'not doing'. This means I am just simply an observer of bodily phenomenon. It goes much deeper than this as one can observe with a kind of gentle organic intuitive processing which is helpful when seeing the threes marks of existence within the skandhas. Many people have given this meditation different names but I don't concern myself with that. Find your own comfortable technique but use Buddha's guidance as a framework. Here's a beautiful quote from the Diamond Sutra that illustrates this message.


  Awakening does not come from a set method of teachings but an internally intuitive process which is spontaneous and part of one's own inner nature.


Here's an audio version of the Diamond Sutra...

https://youtu.be/HK9u7Jz-vNA