SimpleInvite runs in your browser, and you can install it so it opens like an app, in its own window, straight onto your events.
Open the menu under your name and choose Install. Chrome and Edge then ask you to confirm. On an iPhone or iPad, tap Share, then add it to your home screen. Android browsers have Install app in their own menu.
It is the same account and the same events either way, and nothing to update. Your guests never need it; the invite opens in any browser.