Custom Android ROM

Whats your preferable android ROM? Is it secured enough against trouble/exploits?
Currently, I've been trying to safely erase my data concerning multiple overwrites after my smartphone was confiscated by authorities. However, I'm not sure how similar solid state media used in phones is to solid state drives in computers. so I still feel exploited?
In spite of that, I believe getting a new phone's a better solution.
For the meantime, I'm looking to encrypt my phone's storage and is it possible to destroy the keys in case someone tried to recover any data.
Correct me if I am wrong considering I've been out of the game for years.. muchas gracias !