1) Most places use simplified characters. Only Hong Kong and Taiwan are using Traditional characters.
2) I would say you will have plenty of opportunities to practice speaking Mandarin. Beside the local Chinese, you will also frequently encounter Malaysian Chinese and Mainland Chinese who usually speak better Mandarin.
Be prepared for some differences between Singaporean Mandarin and Standard Mandarin.
Differences in vocabulary. Singaporean Mandarin have more loanwords from Malay, English, Hokkien and Cantonese. And some of these loanwords are very integrated. I was shocked to learn that 巴杀 （basha, wet market）is a Malay loanword pasar. Some loanwords from English are 巴士 （bashi, bus) and 德士 （deshi, taxi). Other loanwords from Hokkien are 阿麽 （ama, grandmother), 阿公 （agong， grandfather), and days of the week 拜一 (baiyi, Monday) instead of 星期一 （xingqiyi)
The R endings is dropped in Singaporean Mandarin. For example in Standard Mandarin 饿 （e） vs 二 (er), while in Singapore Mandarin 饿 and 二 （e) both don't have the r endings.
The second consonant h (in zh, ch, sh) sound is dropped in Singaporean Mandarin. The h sound requires the tongue to be curled backwards as the sounds are made. For example, in Standard Mandarin 吃（chi）and 刺(ci), while in Singaporean Mandarin 吃 and 刺 sounds like ci. I am guessing when Singaporeans mean that Standard Mandarin sounds harsh, they are referring to the r endings and the second consonant h sounds.
Differences in tones. Singaporeans just love the second rising tone. Some examples（Standard Mandarin vs Singaporean Mandarin), Father (ba4ba1 vs ba2ba2), Mother (ma1ma1 vs ma2ma2) and other family words. Its my personal opinion but I think the second tone sounds more warm and friendly.
And lastly the Lah, Leh, Lorh, Mah etc endings.