What are the differences between 香港繁體, 澳門繁體 and 台灣正體?
Technically speaking, there are mainly two factors diversifying what you see between different versions of Chinese Wikipedia pages:


The HTML language tag: lang

&lt;html lang="zh-CN" dir="ltr" class="client-js ve-not-available"&gt; 大陆简体
&lt;html lang="zh-HK" dir="ltr" class="client-js ve-not-available"&gt; 香港繁體
&lt;html lang="zh-MO" dir="ltr" class="client-js ve-not-available"&gt; 澳門繁體
&lt;html lang="zh-SG" dir="ltr" class="client-js ve-not-available"&gt; 马新简体
&lt;html lang="zh-TW" dir="ltr" class="client-js ve-not-available"&gt; 台灣正體


The lang attribute tells the browser to choose proper display settings such as fonts and styles. Different "proportions, shapes, and sizes" are generally decided by the browser and the locale settings of the operating system.
Wikipedia literal conversion system "字词转换" (TECHNICAL DETAILS). The necessity of the conversion is that different regions sometimes use different Chinese terminologies, e.g.


  大陆：数字化、数码化 
  台灣：數位化 
  港澳：數碼化 
  新馬：数字化、数码化


The conversion has four stages, which are sequentially executed by the MediaWiki LanguageConverter (a brief history can be found here):


  (1) MediaWiki internal conversion table (MediaWiki内置转换表); 
  (2) Chinese Wikipedia local-global conversion table (中文维基百科本地全局转换表); 
  (3) Public conversion group (公共转换组); 
  (4) Manual conversion for specific entries (各条目内手工转换).


So even if the automatic conversion steps (1)–(3) fail, the final manual work can rectify all the errors.