Nice to here that you are ready to pay…
We have experience in Opentaps ERP (which is fork of OFBiz ERP) and Open ERP.
We have evaluated some Open Source ERP and then finally we are here.
You can see ERPNext vs Opentaps comparison here https://blog.frappe.io/blog/open-source/opentaps-vs-erpnext
Forum post, that will help you to make Features Comparison Documents.
Please share your documentation when you complete, it will help a lot who is searching for good Open Source ERP.