SA for many years suffered from what can be called 10 man rugby trying to regard the backline as of nothing other than defending, In moist provinces were that scoring of tries were extremely low when compared to the New Zealand and Australian teams.
Two reasons for that was what the unlamented coach responsible for some of the malaise said that SA players do not have the ball skills to play 15 man rugby. By the 1992's the efficient backline play pertaining to SA rugby was replaced with what they call "Traditional Springbok Rugby" = that is 10 man rugby, which was unadulterated crap.
There was some efforts made to change back to the comprehensive game SA used to play by Carel Du Plessis and in a recent article an expert stated that Du Plessis was 20 years ahead of his time when trying to introduce comprehensive rugby in SA, Du Plessis established a squad with the necessary skill sets and the squad was remarkedly successful winning winning 17 tests in a row, One of his key players were Percy Montgomery - himself a small guy Du Plessis used as outside center and Mallett moced to full back. So why was it possible - because the so-called :Traditional Springbok Rugby" myth resulted in skill-deficient players selected for teams based on size and bulk.
White to his credit realized that there was something seriously defective in SA rugby and in the 2007 RWC he brought in Eddie Jones to try and see what can be dine to upgrade backline play. After the 2007 RWC some of the players said that Jones taught them things they have never heard about from any SA coach.
After White's Departure 15 man rugby vanished totally from sight, To maintain forward domination the coaches after 2012 especially selected loosies that had zero ball skills and ball sense to make up a Tight 8 and the result was there were no affective contribution by loosies to effective backline play at all. Even Burger lost the abilities that he showed in 2004 when he was the World Player of the Year by 2012.
As a result aimless kicking was the norm and what was most upsetting was that the Springboks was addicted to 10 man rugby and had nothing else to offer.
To his credit Erasmus realized there was a serious deficiency in the game that needed to be corrected, In essence Erasmus did select smaller players too - like Nkosi, Mapimpi and Kolbe to play in the backline - but he also insisted on forwards being ball-skilled and able to link up with the backline in attacks,
Two examples of where it effectively happened were the two tries being scored in the WC Final in 2019, In both two players played a key role - namely Marx in the Mapimpi try and Du Toit in the Kolbe try.
So to come back to the situation raised initially - if the loosies and even Tight 5 players have the necessary ball skills and ability to link up with backline players in attacking moves size of backline players is not all that counts - ball sense, ball skills and pace is very important - provided that all backline players - irrespective of size are sound defenders,
However, a mix between smaller and bigger players are probably the way to go.