Builder track record & RERA: What am I missing?

Been looking for a 3BHK in Bengaluru for months now, it's getting crazy. Currently in a 2BHK in Whitefield, but family badh rahi hai. Thinking of upgrading, maybe a villa near Sarjapur. Builders like Keya Homes, Prestige City, sab dekhe. But yaar, unka legal track record kaise check karein? RERA registration toh dekhta hoon, but usmein kya red flags ho sakte hain? Matlab, only RERA number is enough ya aur bhi kuch dekhna chahiye? Aur agar builder delay karta hai project, toh RERA ke under kya real options hain? Don't want to get stuck, already home loan chal raha hai. Is the premium for a good builder worth it for peace of mind?