I wouldn't be too prescriptive. I have Pro, and it's fine. I'm not an incredibly heavy user (yet?); I've hit the rate limits a couple times, but not to the point where I'm motivated to spend more.

I haven't tried it myself, but I've heard from people that Opus can be slow when using it for coding tasks. I've only been using Sonnet, and it's performed well enough for my purposes.

Sonnet works fine in many cases. Opus is smarter, and custom 'agents' can be set to use either.

I prefer configuring it to use Sonnet for things that don't require much reasoning/intelligence, with Opus as the coordinator.

Opus is slow, so sessions should be used in parallel, likely across work trees. You shouldn't sit and wait on an Opus agent.