I see what you mean about limited options. I looked further and see mostly 800W 120V ER11 spindles or 1500W 240V ER16 spindles. Maybe you have to decide if ER16 is that important to you, then you may need to spring for a 240V power outlet. ER11 is plenty for me with my 800W spindle. I mostly use 1/8" and 1/4" router bits, but have a cheap collet set for the occasional random size bits. I think I purchased it from AliExpress. The price including shipping was slightly cheaper than EBay and they have a lot of vendors.

I believe that the inverters operate similar to a current limiting power supply. They have voltage and current limits. They normally send out the target voltage, but reduce the voltage if the current is too high.

Steve