A: Using GPT-4 for all tiers!
You may probably tweak it a few times, same with under business summary, branding, themes and topics, before you get it exactly where you want it
Put specific ideas under Tone, writing sample so AI will copy your example works and writings!

for BYOK - it's on our roadmap! and i added your inquiry and you can still add more comments, here's the link:
https://roadmap.mymarky.ai/b/1v38qg07/feature-ideas/byok-bring-your-own-ai-key
We’re working on it! Please upvote ideas that works for you and your specific idea in comment will greatly help so you can get notified when its deployed!
more help for us if you will put specific idea in your comments on the roadmap ideas

Please reach out to me through the chat on the website for further ideas and questions! mymarky.ai