Well i got 250 AD Optics going through Monarchy, had pretty decent BPT (~150) and an academy, but everyone except Mansa had Optics. Joao got Astro shortly after that too. I hate when Joao is in these ISO games. He always goes for Optics for his UU and then when i meet everyone half or more of them have Optics because of him. I don't feel like playing on.. considering this one a loss.
I thought 250 AD was still a good enough Optics date to justify the Monarchy detour to get better BPT for teching on towards Steel later, but maybe not. I remember Pedro said he was starting to think that just getting Optics as early as possible is the most important thing in these games. I'm sure there's some limit to that.. like you don't necessarily need Optics in the BCs, but 1AD-200 AD seems like a good target if possible.
Your MC approach may work out better here. How are trades in your game with 1 AD Optics?
FWIW, i reloaded my game back around 500-600 BC and settled the silver as a 5th city to see if it made much difference and i ended up with the same Optics date (within 1T at least). I think the silver allowing all other cities to grow 1 size without building warriors is worth it. The lake + silver tile is OK commerce too.