the correct ones while most likely more expensive will give you much better iops, less latency and much much more endurance.
That may all be correct, but in the end the card reader itself is the bottleneck. Of course, I could overclock the reader, but then the life of the card would also suffer massively. And a NAND SDCard with a reasonable amount of storage space costs a lot of money. The solution via SSD is much cheaper and more reliable.
Same here. Then use Raspiblitz. It has a lot of features 
You can also install Docker there and run the StorjNode.
I’m not quite sure if I understand the question correctly, I use the RTL web interface with VPN or TOR, as my node can only be reached via Onion.
It is safest for me to access it from outside via VPN. I once had the Zeus app on my smartphone in connection with Orbot, so I could reach my node via smartphone via TOR. I think an app is better in the end if you want to scan QR codes and use it to pay or receive. I haven’t tested that yet. I always pay directly from the RTL web interface.