Hi,
You can use below link to check configuration maximums for NSX-T.
https://configmax.esp.vmware.com/guest?vmwareproduct=VMware%20NSX&release=NSX-T%20Data%20Center%203....
A single Edge Cluster can have maximums of 10 Edge Nodes and you can configure them A/A. However, you need to consider ECMP path limits.
There can be maximum of 8 ECMP paths and limit applies independently to Gateway Distributed Router (DR) and Gateway Service Router (SR), i.e. a DR can load-balance the traffic towards 8 different SR, then on a given SR it can have up to 8 different paths.