Hi @Leung1975 , I mainly work with Azure Web Apps so my reply is slightly biased. I would suggest you post your question to the SharePoint community forum as well to receive a well rounded answer.
In regards to web apps, yes either approach that you listed is possible and I've seen customers successfully implement either approach. If you want to avoid the overhead of managing a web app, it might be possible to accomplish this on an Azure Function, which is essentially a server-less web app.