SharePoint Development - Leave Request or Vacation request form

Hello vchack7 ,

I have built a Leave Request application for the company I work for on our SharePoint Online environment using SPFx with React.js and Microsoft Flow. 
I used a combination of SPFx web parts to display some chart and list data, as well as the form to apply for leave and Microsoft Flow to handle the email sending and updating of data on SharePoint lists. For the web parts, I used the Bootstrap library for the style of the forms and so on.

I had this application on the classic SharePoint Online environment, but moved from using SharePoint Designer and classic SharePoint pages as I noticed that there were a lot of bugs and errors on SharePoint behalf that were messing with the application's functionality.

Maybe you can consider this approach? I also distinguished between which was the better choice in this post here: https://techcommunity.microsoft.com/t5/sharepoint-developer/develop-using-sharepoint-add-in-or-spfx-framework/m-p/1109703#M8335

vchack7  You can follow hybrid approach with the MS PowerApps and MS Flow combination for this application.