Six BRRRRs and a flex build is a real base to think from, so let me try to make the comparison concrete.
In a BRRRR you force value, meaning you create equity by improving something that was worth less before you touched it. The return comes partly from that forced appreciation and partly from the rent. In a performing note you buy an existing loan at a discount to its face value. Face value just means the total amount the borrower still owes. If someone owes $100,000 and you buy that loan for $85,000, you collect payments calculated on $100,000, but your actual investment is only $85,000. That gap is where the yield comes from, and it can push your effective return meaningfully above the stated interest rate on the note.
What you are trading away is control over the asset. What you are trading into is a known, scheduled payment stream that does not depend on a contractor, a permit office, or a vacancy cycle. For someone in your position it is worth asking whether the yield is higher than your net on a stabilized BRRRR after debt service and management, and how much of your time that BRRRR is actually consuming.
The thing worth pricing out: your BRRRR returns are partly compensation for execution risk and management friction. A note removes most of that friction, which is why the yield looks lower at first glance. Whether it actually is lower depends on the discount you paid, the note's rate, and the remaining term. Those three numbers drive everything.
I would not frame this as paper versus property. It is a different risk profile: you are a secured lender rather than an owner, and if the borrower stops paying, you end up in foreclosure proceedings, which takes time and money.
The strategy guide on this page goes deeper on due diligence and servicer selection, which are the two places performing note buying either works or falls apart.
What does your current cash flow look like per door after debt service? That number changes whether this fills a gap or just adds complexity.