What I come to understand about Kriyoga is as below.
“Sampurna Kriyayoga Kriya Brahmarupam Kriya,
Sampurna Aadhar Shiva Shakti Kriya Vedarupam Kriya”
Kriyayoga is basically a “Tantra” through which a Kriyayogi gets his internal power awaked in order to reach totality in his life with very spiritual path of knowledge. So, as it is said above a complete Kriyayoga is Absolute way of Brahma which total base is the Kriya (function) of Lord Shiva and Goddess Maa Shakti Jagdamba and they are full of pure Tantra and that is done with Vedic way is a complete Kriyayoga.
There are some Asana with some special Pranayama and Mudra but they do not complete Kriyayoga completely but it gets complete when a Kriyayogi uses Veda Mantra too with Mudra and Pranayama.
Kriyayoga is a very powerful techniques to activate his Kundalini Chakras and other power points situated in his whole body. This techniques/gyana can only be received through a Sadgurudev there is nothing alternate at all and GURUSEWA , SAMARPAN and SADHANA are the main objects to pleased a Sadgurudev to received such powerful gyana.
Mind it, if lacking of pure LOVE one neither devote himself fully to his Sadgurudev nor can serve for him. So how the pure love will be generated in one’s soul that is also a question and the answer is only GURUMANTRA SADHANA and nothing else and a real sadhaka should receive such gurmantra from a real Sadgurudev.
Kriyananda Maharshi Dayananda