3) what's the point?

It's not like the pool of guile developers is much larger than the pool of elisp developers.

And guile has gotten worse for users in the 3.x series compared to the 2.x series.

This is coming from someone whose used it since 1.6 and gave up around 3.0.4 moving to racket.

Guile is garbage, just move to CL

In terms of speed, yes. In terms of functionality, hell no. Compare the following in Racket:

  (define (add-2 x)
    (+ x 2))
  (add-2 z)

Where the result is an error without the possibility to provide a value. Compared to in SBCL:

  (defun add-2 (x)
    (+ x 2))
  (add-2 z)

Where we are dropped in the debugger with the following possible restarts:

* Continue, where we retry the operation (best to first define z),

* Use Value, where we can provide a value to use,

* Store Value, where we can set z to a value and use the value,

* Abort, where we just cancel the operation.

There's also setf expansions, so in SBCL we can do, for example:

  (setf (car some-pair) 3)

Whereas in Racket we can't do the equivalent:

  (set! (car some-pair) 3)