Sorry, I didn't notice you'd already included the PSU spec. My apologies.
If it's the SP-750M PSU tested in this review, it looks like you've made a good choice and it will be more than capable of supplying the RTX 3060Ti.
https://www.techpowerup.com/review/thermaltake-smart-m-750w/
Here is a list of Asus BIOS error codes:
Code B1 = Runtime Set Virtual Address MAP End
https://www.hardwarecentric.com/asus-motherboard-error-codes-list/
This guy had code B1 and discovered his RAM was not fully compatible with his mobo (not a Z97).
https://rog-forum.asus.com/t5/z270/solved-maximus-ix-code-error-q-code-55-b1-cc/td-p/620652
The computer I'm using at this instant in time is as follows:
Gigabyte GA-Z97-D3H mobo and Intel i7-4770K.
Four 4GB (16GB total) Crucial BLS4G3D1609DS1S00 DIMMs at 1600MT/s (DDR3-1600).
Aida64 shows the DIMMs are running at 1.512V (not 1.65V XMP).
Memory Timings are 9-9-9-24 (CL-RCD-RP-RAS) from SPD.
I've applied a medium overclock multiplier of x41 (4.1GHz max) with a manual Vcore voltage set to 1.260V, but Vcore is currently around 0.900V at idle.
The system is stable.
I'm using the Integrated: Intel Haswell-DT GT2 - Integrated Graphics Controller in the i7-4770K, not a PCIe card like your RTX 3060Ti, because my main PCIe slots house an Aquantia AQtion AQC107 10Gbit Network Adapter and a Hewlett Packard SC44Ge Host Bus Adapter for my LTO4 SAS tape drive.
You say your RAM is
Kingston DDR3 8GB RAM 933 MHz x 4 (32 GB total RAM).
Am I correct in thinking the 933MHz refers to the true memory clock frequency, with a DDR transfer rate of 2 x 933 =1866MT/s?
If you're running at XMP DDR3-1866, try backing it down to DDR3-1600 or even stock DDR3-1333. As you're probably aware, memory timings often need to be relaxed when you fit four DIMMs instead of two, due to additional load on the IMCs.
With any luck, you won't get any B1 errors at 1333MT/s. If 1600MT/s is not fast enough for your needs and you find 1866MT/s is unstable, try relaxing the CL (CAS) timing by 1 or 2 clock cycles, e.g. if CL=11 at 1866, increase the value to 12 or 13. It might make 4 sticks of RAM more stable.
You might consider running MemTest86 at 1866 to see if the current timings are stable.