Yes you can. At Daywize we have created an HR application. Each client has its own setup due to different setting options.
In your case it is good to think about which options can be usefull for other customers. So if an extra field could also be usefull for other customers you can make a customer setting for just this field. If some components are only for one specific customer it is more easy because you can then use one boolean setting to make your forms show the extra's or your microflows doing something differntly.
Your hardest part will be creating the rest of the logic multitenant (because you will make mistakes). There are some post about multi tenancy and also make sure to check the documentation and example project in the appstore: https://appstore.home.mendix.com/link/app/80498/Mendix/Multi-tenant-administration
Hope this helps,