1,from my perspective是比in my opinion好一些
其他一些类似说法还有
I maintain that,
From my part,
as far as I can see/as far as I am concerned...
I'd like to point out that...
Although I'm not 100% sure,I still think that...
2 用is 不如 In addition to what has been mentioned above,
语法可参考
as mentioned above是as it is mentioned above的省略,as引导状语从句。
as is mentioned above,as为关系代词,引导的非限制性定语从句。
两者结构不同,但意思表达相同。
另外类似表达还有furthermore, additionally, moreover
3 感觉a greater extent/degree 更常用
4 play更常用