Note that encrypted db stuff generally tries to use weaker notions of security in exchange for performance. Generally research revealed that it was even weaker than the authors thought. FHE is generally something different.

>Does a system like cingulata offers encryption as strong or better than aes256gcm?

One of the security garuntees of aes-gcm is non malleablity. Any attempt to modify the ciphertext is detected. This is the key reason why GCM is popular over older methods like CBC. In homomorphic encryption, the entire point is to be able to able to do arbiteary computations on ciphertexts without decrypting. So even theoretically it would be impossible for homomorphic encryption to give same/better security properties as aes-gcm.