Here’s my take on the TMC2100 drivers after using them for a while AND the DRV8825s.
The TMC2100s are VERY silent when you are in their “silentChop” mode. This is the default mode where it also steps the 1/16 to 1/256 for smooth motion. BUT the “silentChop” mode is NOT made for 3D printers. 99% of the time when using them in this mode they would print fine but they would still skip from time to time. You can make this stop by upping the VREF voltage but then they run hotter and your stepper motors are very warm, I had to run my steppers at almost 1V on the VREF to get them to stop skipping. This made them run at about 70C.
You can switch them to “spreadCycle” mode where they operate like a normal stepper and have the 1/16 to 1/256 translation for smooth movement BUT they are VERY noisy. I have a DC-DC step up converter on my setup for the drivers where I can run anywhere from 12V to 48V. Even up to 36V they were still making a high pitched noise. They did NOT skip though and I was able to use a low VREF and the motors didn’t get too hot. In order to switch them to spread cycle all the CFG pins should be open and you must close the solder jumper on the CFG1 so that it pulls down to ground through the RAMPS board.
What does this all mean? The TMC2100s are good drivers. I also have the DRV8825’s and they are quieter than the TMC drivers when they in “spreadCycle” mode. My 8825s are actually quieter than the TMC2100s and have more torque at a lower VREF.
TLDR; the DRV8825 is my choice for drivers since I do not want any chance of the motors skipping. Save your money and go with the DRV8825’s or the A4988. TMC even says that silentChop is NOT meant for higher torque applications which is what we need for the 3D printers.