• By default, you can fetch only 500 items in PowerApps.
• You can extend this limit till 2000 items from Power Apps settings.
• You can delegate the data processing to the source database and fetch only required row so that it doesn’t take more time processing the data in PowerApps.
• Right now, delegate function is supported only in
  • Dataverse (Formerly: Common Data Service -CDS)
  • SQL Server
  • SharePoint

PowerApps Delegations in detail