While I am always looking for off-market, as an agent with access to MLS, that's my primary source of looking for deals right now. 

Bottom line sub too is an advanced strategy that should only be done by Experienced investor with significant cash reserves or access to lending/like substantial LOC that already exist and can be taped at a moments notice. 

They "may" have access to some off-market listings, which aren't on here or the MLS, but in regards to info there's absolutely not a thing.

With online access to almost every jurisdictions property recordings, lenders today use software that automatically searches property transfers for transfers involving their loans.  

Most importantly, their platform is not user friendly and has a time consuming learning curve.

Hard money is expensive.Some questions to ask yourself to assess risk:Do you have access to a reliable contractor who can complete the work on time and stick within a budget?

They do local meetups but you can at least gain access to true off market properties as apposed to using wholesalers.

are there any other platforms for such listing? 

Imagine a platform like Zillow, Redfin, Trulia, etc. where the seller can market their property while receiving assistance in offer recognition/negotiation.

Focus on STR-friendly areas like Newburgh or Highland Lakes, and use platforms like AirDNA to assess revenue potential.