Raja Yoga is complete, and in my opinion it is indeed very close to the eightfold path. At least it has helped me a lot. Its model of perception is based on Samkhya, and to "interface" with Buddhism without being slaughtered (the yoga side seems to be easier on those matters) you will have to somewhat map "Purusha" on "ku" and "Prakriti" on "Shiki". Or as D.T. Suzuki wrote "Shih" and "Li". Or "The absolute" and "The relative". Apart from that you will basically find the 5 Skandhas described in Prakriti.
Unless you´re going to be a Bhakti Yoga follower who approaches the absolute by devotion that shouldn´t bother you too much.
If you´re not into the physical or breathing part at all, you may try to jump for Jnana-Yoga, and if you want a purist, fast-track version of this, look for the Advaita-Vedanta people.
There are some aspects in Raja Yoga which nowadays seem to be somewhat neglected, like Pratyahara, since most western Yoga "systems" tend to heavily focus on the physical path, which for Raja Yoga is not really that important, or jump into Dhyana, because something can be imagined for that concept, then it is some sort of meditation practice. Pratyahara in my experience is the key to combine the two, the hard work that has to be done or nothing will work. Where you see whether what you think you have understood will prevail in practice or not. In buddhist terms you would say there you become aware of defilements arising and work your way through "handling" them. A prerequisite for concentration.
For Raja Yoga you basically need an asana to be able to sit in meditation, that´s it (you can of course do more, there´s some exploration that can be done). The rest is inner work, to recognize the workings of the mind, body, consciousness. Does sound familiar ...
You may want to read through "Raja Yoga & Patanjali Yoga Sutra" by Swami Vivekananda.
One aspect which I found is seldom emphasised is Pratyahara. Personally I found Pratyahara to be essential to really be able to start to get a grip on the workings of the mind.
It helps to pick something where you really have a "burning desire to master it". That art usually searches you, you don´t have to look for it, you already know what it is. It will then provide you with all those emotions that have to be overcome on the path to mastering it, and the necessary motivation for the practice. That must not necessarily be the yoga itself. It can be whatever, and complementing that with the yoga will make your art the vehicle with which you practice your yoga.
Making the yoga the object of your yoga in my opinion bears the same risk of struggle as wanting to become enlightened.
But I suppose you´ll have to work your way through one of these
You may look for some videos of Swami Satchidananda on the web. Most things I have found from him are pretty solid, he appears to be speaking from the center and not for primarily profit purposes.