The major difference between evolutionary coaching and normal coaching lies not in the skills and practices, but in the approach and purpose. The skills and practices needed for evolutionary coaching are the same as those used in all other forms of coaching: connecting, listening, clarifying expectations and objectives, suspending judgement, identifying feelings and beliefs, etc. What is different is the understanding that the framework of psychological development brings to the process of coaching. Without this framework we would not be able to understand the deep underlying needs of our clients.
Evolutionary coaching helps people understand what stage of psychological development they have reached, how well they have mastered the stages of development they have passed through, and what stages of development remain for them to master.
The stage of psychological development you are at affects every aspect of your life. It affects your needs, your values, and the relationships you have with your family, your co-workers, and with everyone you interact with on a daily basis. When you understand where you are in your development and what stage is coming up next, you can make choices that anticipate future challenges and thereby accelerate the pace of your development.
When you know your needs and values will change as you grow and develop, it helps you to see your life differently; it gives you an evolutionary perspective. If you know that your needs in the future will be different from the needs you have now, you can look out for opportunities to not just satisfy your immediate needs, but also for opportunities to satisfy your future needs too.
In other words, instead of having just one set of lenses to see the world through—the stage of psychological development you have reached—you can catch a glimpse of what your life might be like if you looked through the lenses of your next stage and subsequent stages of development.
The framework of psychological development also helps you to understand what stages of development the organisation, the community and the society you are embedded in have reached. The stages of development they are at not only affects their values, it also affects the relationships they have with their stakeholders and most importantly their ability to meet your needs at the stage of development you have reached.
It is vitally important for you, as a coach, to explore with the individuals you are coaching the extent to which the culture of the organisation, the community and the society in which they are embedded, support them or hinder them in meeting their needs.
If the cultures they are embedded in hinder them in their developmental journey you may need to help your clients develop an exit strategy: help them find an organization, community or society that will be better able to support them in their human emergence.
If, on the other hand, the cultures they are embedded in support them in their developmental journey then you should impress on them that their best strategy for success is not to focus on satisfying their own needs but on satisfying the needs of organization, community or society in which they are embedded. This requires a shift in personal focus from caring about the needs of “I” to caring about the needs of “we”.
The key difference between performance coaching and evolutionary coaching: Performance coaching is about helping people meet the goals they have at the level of psychological development they have reached. This is the domain of the business coach, the sports coach, the voice coach and any other type of coach who is focused on performance with a little “p”. As a performance coach, you just have to be good at helping people get better at doing what they do. It does not matter whether you, the coach, have self-actualized or not. Obviously, if you have self-actualized, and coaching is your passion, this will support you in becoming an excellent performance coach.
Evolutionary coaching is also about performance, but performance with a big “P”. Performance with a big “P” is about human emergence; not just helping people become more proficient at what they do but helping them to participate in their own evolution and get better at being as well as doing. This is the domain of the leadership coach, the executive coach and the life coach.
Only when you have lived through your own emergence—completed your individuation and self-realization—can you bring wisdom to bear on the process your clients are going through.
Evolutionary Coaching 
You mention big “P” and little “p”. I like the way Tim Gallwey puts in his formula and graphic.
The Formula is P = p – i. Big “P” is potential, let’s say fully evolve to “service”; little “p” is performance, let’s say where you are now; and i is interference. Picture the graphic of a triangle (delta sign for change) with a capital “C” in the middle which stands for coaching. The formula is the top point; the lower left hand point is “enjoyable” and the lower right hand point is “learning”.
This is how I explain coaching around the definition of “bringing a valued person (you!) from where you are to where you want to be.” I have a more “clinical” definition as well.