For the North-South (to Internet) throughput, it would be depends on your environment
vRealize Network Insight would be helpful to capture this so you can understand what will be the requirements
As mentioned in other reply above, you can always use ECMP up to 8 NSX Edge if that is an option
Other concerns will also depend on use cases.
One of the roadblocks in my customer is they have an application that runs on physical hardware servers that need to sit on the same L2 network with VMs and stretched across Datacentre.
MTU over WAN can be a roadblock if there's a constraint there.
Then stretched VXLAN (Universal Logical Switch) doesn't support L2 bridge as far as I know at the moment.
So my customer use other L2 stretched network technologies (EoMPLS or Cisco OTV or something else) that runs on defaut MTU 1500 and works with physical hardware servers
The customer also does not deploy VXLAN and only use NSX DFW for that particular application