I do recognize the GR is an extreme case and hopefully we do not experience anything similar to GR.So their theory does not match my reality as someone who actually had well established STRs at the GR.I suggest you be leery of people who present theories without any experience related to their theory. 

Possibly riskier because the businesses are less established (of course I must do my proper due diligence.)With my long time horizon before I plan to use the money, it's possible that the higher rate of return for syndications would offset the initial higher tax hit. 

Build a Team: Surround yourself with a reliable team, including a real estate agent, contractor, property manager, and financial advisor.

That's the way it was explained on another Solo 401k advisors webinar.

Should I establish an LLC and close in it at this stage of my investing journey?

I would recommend that you first Identify a strategy and make sure that the market you choose that aligns with it then establish your Core 4 Real Estate Team. 

Especially if they are established tenants.

So would potential tenants look at that and think they wouldn't want to rent the property becasue of that, even with it being in a "nicer well established" neighborhood?

You may also try to stop by your local Bank of the West branch - better than trying to establish a relationship by phone - to see if they offer investment HELOCs in TN.

BREIT by blackstone is private, not publicly traded, and is only sold by blackstone chosen financial advisors, it has 4 different class shares and most have huge load fees (1.5-3.5%) and yearly AUM fees (1.25%), and if you sell <12 months from any share purchase they charge you an exit fee of 2% of NAV price , so be careful with that oneI've invested in many syndications for passivity/market beating returns/tax benefits currency debasement running at 15% a year since GFC(2008), (ie M2 money supply growth) so you have to get >15% just to tread water in USA now