Higher stroke rate, more kicks = increased effort - always.
Stroke rate and stroke length are based on height (wing span), skill set and swim distance (what you can sustain)
When in doubt what to do - just do the math:
SL = 1.3yards (15 spl)
tempo = 55 stokes per minute or 1.09 seconds per stroke
speed = 1.3y x 55spm = 71.5 yards per minute
100 pace = 100/71.5 = 1.399 mins = 1:23.94
SL = 1.05yards (19 spl)
tempo = 70 stokes per minute or 0.86 seconds per stroke
speed = 1.05y x 70spm = 73.5 yards per minute
100 pace = 100/73.5 = 1.36 mins = 1:23.0
However if you can sustain 70spm and drop a stroke to 18 spl, 100y pace would be 1:18. Dropping a stroke at any rate yields the quickest results to faster pace.
Do the math, find out what stroke rate, stroke length combination will get you to your goal(s).