A. I have joined MNC in July, and have learnt one thing, your knowledge and experience add weight to your CV and not any additional course/degree/certificate. So, definately, dont go for further studies, if you are a qualified CA. Yes, after joining any company or starting with your career, you can join any course, depending on your interest and requirements.
B. If you dont have much exposure, thn i would suggest you to go for some SME (corporate ofcoarse). As, once you join CA Firm to gain experience., that will disturb you in getting job in any company in future. So, i would suggest you to join any SME company.
C. And, even if you join any big company, no need to get scared. Generally, the knowledge and experience we gain in our articleship is not that helpful in the companies. The atmosphere and duties change in company, so every company gives some sort of basic training initially., and later, it all depends how you start learning, and execute your knowledge.