I have added in the right margin (scroll down to “download PDF”) a new translation of Patrul Rinpoche’s instruction on the two truths (auch auf deutsch!). It has been translated in the past, but I think that I was able to add some precision to the translation. I also provided a number of footnotes to clarify a few points for those who have not so much experience in reading this kind of text.
Although I do not know of any systematic presentation of Jigten Sumgön’s understanding of the two truths, I think that Patrul Rinpoche’s explanation is very close to how Jigten Sumgön would teach them. The main point is that the level of truth is determined by the realization of one’s mind. Thus, already Jigten Sumgön’s guru Phagmodrupa had said (as quoted in Rigdzin Chökyi Dragpa’s commentary on dGongs gcig 7.1):
E ma ho! This king that is the mind,
– if one realizes it, that is nirvana,
if one does not realize it, that is the ocean of samsara.
Apart from realizing and non-realizing
there is no obtaining and non-obtaining of the fruit.
Therefore, Chökyi Dragpa said in the same commentary: “Samsara and nirvana have no other difference than ‘realized’ and ‘not-realized.'” Moreover, since that realization of the mind is free from all extremes of proliferation – the buddhahood that is achieved in the sameness of all phenomena, the inseparable union – within that absolute result there exists no distinction between the two truths (dGongs gcig 7.1). This union on the level of absolute truth is also in accordance with Patrul Rinpoche’s instruction.
I hope you will enjoy the text!