I have not done this in ongoing project, hence i m looking for some advice.

IF a client already using contact object and has 10-20-50 K records with validation rule, trigger, process builder , flow , workflow etc build on contact objects 

then decides to use person account and enables it 

QUESTION : DO we have to re build ( validation rule, trigger, process builder , flow , workflow etc ) on person account / account with person record type and re configure all automation ( validation rule, trigger, process builder , flow , workflow etc) and objects looking up to contact Objects in ERD ?

I m getting the data migration part . but needs some advice on Metadata part .  any advice/ document would be appreciated

Requirement : Bi-Directional Document Sync between salesforce and sharepoint

* Document should reside in Sharepoint ( upload directly in sharepoint or moved from salesforce) 

* Residenct document in sharepoint should have tracable link published in salesforce under relevent object 

Requirement is : Files upload in salesfore via Email-to-case Attachment OR Document under Record (Account, case, custom object etc.. ) 

should be moved in External document storage (Sarepoint ) with a link to track back in salesforce 

if Document gets uploaded irectly in sharepoint , then it shpuld inform salesforce with the document link under relevent object (might need some folder structure , or Entity identification ) 

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is there any prefered ISV or component or custom code , which could manage Record structure in sharepoint and build bi-directional SYnc with Document residency in sharepoint and link published in salesforce