As the two regions run in different social systems, the vocabularies are different as well.
Let me show you some of the examples:
1. Power Bank
Guangdong: 充電寶 chung1 dihn6 bou2
Hong Kong: 尿袋 niuh6 doi2
2. Mouse
Guangdong: 鼠標 syu2 biu1
Hong Kong: 滑鼠 waahk6 syu2
3. Monitor
Guangdong:屏幕 bihng4 mohk6
Hong Kong: 螢幕 yihng4 mohk6/ 芒 mon1
In financial sectors and IT industry, Hong Kongers prefer copy the English words directly and Guangdong citizens prefer copy from Mandarin. So, sending a email, printing a A4 size picture would be different.
Guangdong:發郵件畀我 faat3 yau4 gin2 bei2 ngoh5
Hong Kong: send封email畀我 send fung1 email bei2 ngoh5
Guangdong:打印一張A4相 da2-yan3 yat1 jeung A sei4 seung2
Hong Kong: print張A4相 print jeung1 A four seung2
We can accept both standard pronunciation and Cantonese-style pronunciation. And most of people would prefer skipping the ending sounds. So ngoh5 我print would be read as ngoh5 prin.
For your second question, as most of people in Hong Kong are used to using English(although with Cantonese-style). It is quite strange to translate into Chinese characters.
Furthermore, Hong Kong is writing traditional Chinese, so for those terms we will probably follow the Taiwanese Chinese words rather than mainland Chinese words. For example, in Taiwanese Chinese print is 列印liht6-yan3, in mainland Chinese it is 打印 da2-yan3.
And also email in Taiwanese is 電郵dihn6-yauh4, in mainland it would be 郵箱yauh4-seung1. In Hong Kong, most of people would used the Taiwanese Chinese translation when we can use Chinese word only.
And Phil, I think we usually pronounce original English tones in the middle of Cantonese sentence, unless we completely change such English words to Canton Chinese words then words would carry tones.
E.g.: I want to take taxi.
我想 take taxi （original English pronunciations)
我想 搭的士 (daap3 dik1 si2) --> have Cantonese tones
