Nitrous as in "Nitrogen" or what? You should have made your question more comprehensible by making a short post about it on the question post box. I will try as much as possible to provide you with the answer according to my level of understanding as regards to your question.
Nitrous site prevalent in steem engine are projects or tokens built on the steem blockchain. This implies that the tokens you see on your steem-engine wallet can automatically be converted to Steemit tokens because they are stored on the steem blockchain.
The implementation of SMT we bring more understanding to this even though we now have lot of tokens on the steem blockchain being stored in steem engine. The steem engine website is mostly used for storing, transferring and receiving these set of tokens built on the steem blockchain.
Thanks for reading and I hope this helps.