2. Most quick general purpose questions like "What is 4-month sleep regression in babies?" go to GPT-3.5
3. If I want to deep dive on a topic, I find myself either using one of the custom GPTs (Grimoire is great for coding), or increasingly, talking to it via voice chat. It's particularly great if I'm walking around the house doing chores and want to learn something I would otherwise turn to Wikipedia for (say, the successors to Genghis Khan and the various Khanates).