As for the weight, Check with the manufacture! They can tell you what tension/weight the top is designed for... Some guitars are built to sound best with mediums and some with lights. Putting lights on a heavier built guitar will lesson the responsiveness, and putting mediums on a guitar designed for lights can cause major structural issues! Always check with the manufacture!
Tone is so subjective and what I like you may not, so I'm not going to try to tell you what's best for you. Just try different brands and compositions till you find the ones that suit your style and guit...
As a side note... Don't get too hung up on string weight (light,xtra-light,medium,etc...) every brand has different tensions for their strings... Some brands xtra lights have the same lbs of tension as others lights, some mediums will feel like another brands lights as well. You can find string tension charts online that will tell you which brands carry what tension.
Here's a quick breakdown of some of the more popular brands and their strings lbs of tension at various tunings..
This first section is using D'Addario strings:
STANDARD TUNING E A D G B E TOTAL
LIGHT 26.0 29.9 30.5 30.2 23.3 23.3 163.2
MEDIUM 29.0 34.0 36.8 35.3 26.3 27.4 188.8
HEAVY 31.9 38.8 44.7 38.0 29.3 31.5 214.2
TUNED DOWN 1/2 STEP D# G# C# F# A# D#
LIGHT 23.2 26.6 27.2 26.9 20.8 20.8 145.5
MEDIUM 25.8 30.3 32.8 31.5 23.4 24.4 168.2
HEAVY 28.4 34.6 39.8 33.9 26.1 28.1 190.9
TUNED DOWN FULL STEP D G C F A D
LIGHT 20.6 23.7 24.2 24.0 18.5 18.5 129.5
MEDIUM 23.0 27.0 29.2 28.0 20.9 21.8 149.9
HEAVY 25.3 30.8 35.5 30.2 23.2 25.0 170.0
DADGAD D A D G A D
LIGHT 20.6 29.9 30.5 30.2 18.5 18.5 148.2
MEDIUM 23.0 34.0 36.8 35.3 20.9 21.8 171.8
HEAVY 25.3 38.8 44.7 38.0 23.2 25.0 195.0
OPEN D D A D F# A D
LIGHT 20.6 29.9 30.5 26.9 18.5 18.5 144.9
MEDIUM 23.0 34.0 36.8 31.5 20.9 21.8 168.0
HEAVY 25.3 38.8 44.7 33.9 23.2 25.0 190.9
OPEN G D G D G B D
LIGHT 20.6 23.7 30.5 30.2 23.3 18.5 146.8
MEDIUM 23.0 27.0 36.8 35.3 26.3 21.8 170.2
HEAVY 25.3 30.8 44.7 38.0 29.3 25.0 193.1
NOTE: FIGURES SHOWN ARE IN LBS USING A 25.5" Standard] SCALE LENGTH
FOR A 24.75" SCALE LENGTH MULTIPLY TENSION FIGURES SHOWN BY 0.95
FOR A 24.90" SCALE LENGTH MULTIPLY TENSION FIGURES SHOWN BY 0.96
FOR A 25.25" SCALE LENGTH MULTIPLY TENSION FIGURES SHOWN BY 0.98
FOR A 25.40" SCALE LENGTH MULTIPLY TENSION FIGURES SHOWN BY 0.99
For 12 strings:
Martin 12-String 80/20 Bronze Extra Light Acoustic Strings
D'Addario Phosphor Bronze Acoustic Guitar Strings - 12-string Light
010/010 014/014 023/008 030/012 039/018 047/027
Standard tuning: 258 lbs.
1 halfstep down: 230 lbs.
2 halfsteps down: 205 lbs.
Elixir Acoustic Guitar Light 12 String
010/010 014/014 023/009 030/012 039/018 047/027
Standard tuning: 262 lbs.
1 halfstep down: 233 lbs.
2 halfsteps down: 208 lbs.
D'Addario Phosphor Bronze Acoustic Guitar Strings - 12-string Extra Light
09/009 013/013 021/008 029/011 036/016 045/026
Standard tuning: 224 lbs.
1 halfstep down: 200 lbs.
2 halfsteps down: 178 lbs.
Dean Markley Bronze 12-String Acoustic Guitar Strings - Medium
.012/.012 .016/.016 .026/.010 .034/.017 .044/.024 .054/.030
Standard tuning: 366 lbs.
1 halfstep down: 326 lbs.
2 halfsteps down: 291 lbs.
Martin Marquis 12-String 80/20 Bronze Light Acoustic Strings
.012/.012 .016/.016 .025/.010 .032/.014 .042/.020 .054/.030
Standard tuning: 330 lbs.
1 halfstep down: 294 lbs.
2 halfsteps down: 262 lbs.
Elixir Acoustic Guitar Heavy 12 String (for C# tuning)
.013/013 .017/.017 .030/.014 .039/.018 .047/.027 .056/.035
3 frets down: 323 lbs. Surely no one tunes these up to standard. We'd have heard their guitar imploding.
Elixir Acoustic Guitar Medium PolyWeb Coating (6 string)
.013 .017 .026 .035 .045 .056
Standard tuning 192 lbs.
Other manufactures specs are available online....