Don't want to use the Out-Of-Box PowerApps form but yet have the flexibility to save your data to a SharePoint list? Look no further, this blog walks you through the Patch function available to save your items to a SharePoint list. This is a no code solution blog and hence will not focus on the Metadata and Choice with multiple select checkbox columns. Here's the link to blog:
https://powerusers.microsoft.com/t5/PowerApps-Community-Blog/Building-PowerApps-from-scratch-Use-Patch/ba-p/66276
