It is best to try a subscription instead of the API; subscriptions are always cheaper than the API, regardless of which LLM you use.(However, the additional quota will be reset today.)

Subscription are cheaper than API prices, so probably better to go 2nd Pro sub.

But FWIW, ChatGPT 20x plans aren't available right now, see: https://www.reddit.com/r/OpenAI/comments/1wctjkx/tibo_pauses...

And FWIW, if/when the 20x plan comes out, you can consider getting a Pro 5x plan first to see if you can fully utilize that. Upgrade that second account Pro 20x if you need it. Saves you $100/mo.

Learned this the hard way yesterday. Spent $250 on tokens that ran out after just a day. Meanwhile my $100 sub lasted me a week with the same exact work