yes it is permissible to recite naas in first rak’ah and ikhlaas in second rak’ah. There is no specific order to be followed when reciting surah after suratul Hamd.
Yes, it is an obligatory precaution that if you recite surah Ad Dhuha, you would have to recite Surah Inshiraah as well to follow it up. Also, if you recite Surah Al Feel, you would have to recite Surah Quraish following it, in the same rak’ah, after the recitation of surah al Hamd.
Saqalain Abbas Alawi