For Steemcoinpan (SCT), TripleA (AAA) and Palnet (Palcoin) that I know of the platform, you need to stake their token on Steem-Engine, Staking is similar to how we power up steem to become steem power. If you have them the tokens and they are not staked you can earn from curation in SCT when you upvote a post tadged with sct though you'll earn curation on the Steen side of the platform. The good news is that unstaking takes a shorter time, the longest i've see so far is 4 weeks unlike steem where power down takes 13 weeks. Yes, there are various ways you can deposit and withdraw on Steem-engine, but i've only been using the Steem crypto for deposit. You can trade on Steem-Engine the same way you trade on other exchanges.
I haven't had any problem with them at all.
"No answer from Steem-engine yet...." What section did you ask your question?
Have you thought about a Discord channel for @upvotebuilders? Yes, a lot of times but... I'll have a better answer when the time is right my dear friend.