Platform specific design starts with the philosophy behind the platform. Before you drag a single card into a Subsplash list, get honest about what an app is actually for and who it is actually for.
Think about how you engage a website versus an app. A website is where you go when you are looking for something you do not yet have. You are shopping. You are evaluating. You are new. An app is the opposite. You already picked the product. You already have the account. You open the app to check your balance, not to be sold.
The bank analogy makes this clear. Your bank website exists to convince someone to open an account. It talks about rates, features, benefits, and locations. The bank app skips all of that. It opens to your balance and your recent transactions. You are already a customer. You do not need the pitch.
Your church website has to attract new people who do not know you yet. Your Subsplash app does not. Members downloaded it because they already chose your church. So build the app around what they need on a Sunday morning, on a Wednesday night, and when they open it in a parking lot before small group. That is watching last week's message, finding the events they said they would attend, jumping into the group chat, and giving.
Stop trying to make your app a smaller copy of your website. When you do that, you end up with 12 tabs of information a member already knows and cannot find the one thing they opened the app to do. Design for the balance check, not the sales pitch.