TIP: Generally, you ask one question per Question & Answer thread. Though, a multifaceted question and/or questions which are closely related are fine.
1. How to use either() with <<timed>>.
You need to concatenate the string "s" to the value returned by either():
<<set _random to either("1","2","3") + "s">>\
Unless you need the _random temporary variable later, you could simply things by using a backquote expression right within the <<timed>> so that you don't need the variable:
<<timed `either("1","2","3") + "s"`>>
2. Can you start a <<repeat>> immediately?
No. Though you may simply repeat the code once before the <<repeat>> to achieve the same effect. For example
/* code (initial run) */
/* code (repeating run) */
If the code in question is lengthy, consider turning it into a widget to keep things tidier.
ALSO: You called <<repeat>> a loop, which is incorrect. While it does loop, in the sense that it repeats, it is not a proper loop (see: <<for>> if you actually need a loop).
3. Counting words.
Until you know you need something more complex, I'd try something simple like the following, which splits the string on whitespace and returns the length of the resulting array: