Hi @aaroh_bits
Welcome to the power pages forum.
FYI. Power Pages pricing is not yet available. Your screenshot indicates the Power Apps Portals pricing.
For your question,
Q1: Answer: if you want to utilise the mycompany.com landing page then you can iframe the landing page. But you need to configure some security settings to avoid CORS issues. or you can rebuild the home page in Power Pages to keep everything in one place.
Q2: Answer: For your internal, you can either purchase a power app per app plan or per user plan, depending on your need. For external unauthenticated, you should purchase the necessary page views capacity across all portals instances that cater to anonymous access scenarios.
Example: If you are anticipating 400,000 page views per month, then you should purchase 4 lots of page view capacity(unauthenticated)
Hope it helps.
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