At the risk of starting a long discussion.....
1:76 and 1:72 are SCALES; "20mm" is a vague description of a miniature figures SIZE depending where you measure to and from.....
In addition, 20mm figures come in various styles, from chunky to slight to anatomically correct.....
Platoon 20 are an older range as are the original dollies for Liberation; both are small but chunky...
The plastics mentioned are according to Plastic Soldier Review on the small end of the spectrum.
1:76 scale is 4mm to the foot whereas 1:72 is 1" = 6 ft. 1:76 grew out of model railway British OO gauge, 1:72 from model aircraft. Hence you sometimes see 25mm described as 1:72.
In 1:76, a 6' man would be 24mm tall, 5 '6" 22mm tall.
There is also aesthetics. 1:72 will lend to be larger models; some 3D 1:72 prints are huge and probably overscale. If you like your vehicles large compared to figures, go 1:72.
For Falklands, Scimitar and Panhards will be quite small anyway. Airfix do some vehicles suitable, but they are 1:76 despite the 1:72 label - thinking Scopion and ex-JW Landies and trucks....
Neil