I got ahold of a BLDC dev kit (moteus) and tried it out. It is indeed the motor most suitable for human x robot interaction since it is light, backdriveable, powerful, available, long-lasting, and has a large platform of hobbyists doing development work right now. These beat shape memory actuators in precision and ease of use by miles. There's no working fluid, no compressors, no pumps or tubes, and they are ready to have many types of controllers bolted on right from the factory. This is the fastest way to build a good strong motor that isn't a non-backdriveable geared DC motor.
The main downsides I'm noticing are that they aren't very cheap at 30-70$ for just a small low torque motor, 60-80$ in controllers per actuator, up to 500$+ for a geared high torque actuator. Also, there's effects at play that make the motor/actuator system surely undesirable for some people:
>bulky circular shape
>cogging (motor has intermittent torque when the magnets align with the poles) which feels like it has "cogs" as you turn the motor with your hand (not perfectly smooth rotation like you might want)
>noise (quiet static and grinding noise from electronics)
>rigidity by virtue of being solid
>backlash if using a gearbox with small motor
>high inertia if using a big direct-drive motor
If you don't care about the trade-offs, I'd recommend a BLDC + Controller system. I have a gearbox in the works to bolt onto the motor to see if 3d printed planetary gearboxes will work. I'd also like to see if there's a coreless/ironless/slotless motor that would be able to direct-drive a large surface (thighs) smoothly.