Some Magento app builders build the app on your existing storefront, and others connect to Magento through a module or API to build a separate native app.
Check what carries over from your store. MobiLoud and Twinr build on your live site, so your extensions and checkout work as they do on the web. JMango360, Reskyt and Shopgate build native screens through a backend connector, so confirm support for each extension you rely on.
Confirm the price for a Magento store, not a Shopify one. Shopgate supports Adobe Commerce from its Growth plan at €799 a month, SimiCart builds Magento apps as quoted custom work, and MageComp's listed plans are for its Shopify app.
Look for B2B features if you sell to trade customers. JMango360 supports login-gated catalogs, customer-specific pricing and volume ordering. Unbound Commerce builds wholesale ordering apps with order guides and sales-rep modules, and Shopgate adds B2B features on its Enterprise tier.
Check what the price scales with. Apptonize sets its plan by the revenue the app brings in, Shopgate by app sessions and MobiLoud by monthly active users. Unbound Commerce charges a project fee for each build instead.