Best use of Self Directed IRA

[Victor Robinson]

So my standard rei strategy is buy and hold rentals.  That works for me a my goals for a number of reasons.  One reason is that it fits well with my also having a full-time W2 career. 

In my W2 world, I am in the process of going to work for a different company and will have about $40k in an 401k that I will need to move elsewhere.  Not a huge chunk of money, but it's something.  I'd like to move those funds into an SDIRA (or Solo 401k, still not sure of the difference) and use them to engage in a different rei strategy - one that can offer a higher return than buy and hold, but likely doesn't carry the tax and leverage benefits. 

I've thought about private lending with a local flipper.  I'm also considering tax leins and note investing (although a little nervous as I'm less comfortable with the due diligence that would be required for that type of investing).  I'm also interested in syndications and the Fundrise platform. 

I would love to hear what the BP community thinks about the benefits of these different when the source of funds is a SDIRA of about $40k and I'm not interested in tax benefits.

Thanks in advance.