Facebook prefers to keep users on-platform, so posts that send people away (external links) often get less reach than native video, images or text. A common workaround is to post an engaging native update and drop the link in the first comment instead of the caption.
Use both. Your Page is your public storefront and ad hub; your Group is where organic reach and community actually happen. Groups notify members of activity and consistently out-reach Pages, so funnel Page followers into a Group tied to your niche.
3–7 quality posts a week works for most Pages. More important than frequency is consistency and mix — rotate video, image, text and the occasional link so the algorithm and your audience stay engaged rather than seeing the same format repeatedly.