I got 321 marks, what's the chance of getting ECE at Hyderabad? I also got 99% in Mains so far, What would be better option?

I suppose youre relating to your BITSAT Score of 321. Yes with 321, you have fair chances of securing ECE at BITS Hyderabad, as well as ECE and EEE at BITS Goa. You even have slight chances of securing Electronics and Instrumentation at BITS Pilani and fair chances of Mechanical Engineering at Pilani Campus. Incase, youre interested in pursuing ECE, I would perhaps suggest you to prefer BITS Goa first, followed by Top NITs, if any you get at your Percentile/JEE Main Rank. With 99 Percentile in JEE Mains, assuming youre from General Category, youll get ECE at some of the Tier 2 NITs, like MANIT Bhopal, NIT Kurukshetra, SVNIT Surat, NIT Jamshedpur, NIT Durgapur, Patna, Electrical at VNIT Nagpur, Jaipur & Calicut, Mechanical at NIT Rourkela and Allahabad.

Most of these NITs have Good Placements as far as ECE or any other Branch like Mechanical or Electrical is concerned and even comes at a much lower tuition fee comapred to BITS P,G,H, with definitely the Government College Tag to itself. Hence, its totally upto you, incase youre going to BITS, prefer BITS Goa ECE over Hyderabad and Other NITs.