Hi there @contemplate, there are many ways of looking in the two, various authors have illustrated some great work on the concepts of self-improvement and self-actualisation. for me personally i look at the both of me intrinsic, it really comes from with in you. for starter lets take self actualisation, A person can only self actualise when the individual has found deeper value and higher purpose in life, but to acquire this the individual must have the basic needs in life, this is food, shelter, love and sense of belonging in life and a purpose. for example an orchestra artist can only reach his true potential once all his basic needs in life are met, the end goal towards self actualising is reaching your true potential in life acquiring the highest from of knowledge, skill, or success. this is not a challenge by any means, it is has been said that even the mentally ill can reach self actualisation, you simply do not have to have the everything good in life to self actualise, but to once you begin to relaise what yor are capable of by harnassing your true potential, when yourself being more than just a normal person, than you truely have self actualised.
The act of self improvement i see this as a way to better yourself by ego or by self esteem, maybe the right term is self reflective that what you really need to do in life. I don't know but many people don't relaise this each day in your life you are self improving, Your life is learning curve, you see you only have to expereince the mistakes that you have made and think that is not something you should change yourself, but the opportunity to learn and acquire knowledge, that is the only self improvement once can have.

Feel free to ask whatever question you have.
Best regards