Servo Motor Hookup with Gecko's

Still planning the motor setup on my BP project and can't decide on
steppers vs servos. I am leaning towards servos for all the stated
reasons but am hesitant because of the complexity. Assuming I'll be
using Gecko drives, servo motors with integral encoders:

1)What's the main fifference between the 320 and 340? When would
youu use one instead of the other? Is one harder to set up? I
downloaded the manuals but the only material thing I saw was the 340
is PLL (which doesn't mean a whole lot to me!)

2)In the manuals it talks about testing everything with an
osiliscope, etc. Is all of that required? How hard is it really
(without the use of any special electronic equipment)?

3)If I chicken out and go steppers, does it add any benefit to also
run encoders? Do the Gecko stepper drives accept encoder feedback?

Mark