A couple questions regarding AD:
1) For AD integration, is there any issue if I join the PSCs to the domain and then use AD integrated authentication or should I be avoiding that and using LDAP? Currently using AD joined VCSAs in non VCF environment. Down the road (say VCF 4.x) when I imagine the PSCs will be converged, will there be an issue with having to join the vcenters to the domain as part of this process whereas LDAP might be less problematic?
2) Can I join ESXi hosts to an AD domain or will that cause a problem?= with SDDC manager?
1. There is no problem if you join PSC or vCenter to domain using AD integrated authentication or using LDAP. About VCF 4.x environment using External PSC and later you converge as embedded there is no problem to join vCenter to domain.
2. ESXi you can join to domain without any issue. there will be not impact.
3. PSC and AD integration available in VCF 4.0
3. I would suggest you to use VCF guide as best practice.