In the following table you will find which is the best armor mix you can have for a given strength (i.e. encumbrance).
You should try to get those armor sets, as it will give the best ratio (therefore armor efficiency) protec/encumb.
For the same strenght, several combinations of equipment give the same result, so you have the choice.
You'll notice, that the recommendation can change when you get +5 stength; whereas we recommand that you always have the most efficient armor, it's obvious that you can't change it everyday, so just do it regulary.
NOTE: It's not a problem to have some 'extra' emcumbrance points because it will make you a bit faster (better ratio speed/encumb ) so don't get an armor piece just because you can wear it, if it doesn't optimize your armor.
I hope this is all clear :)