Please keep in mind that if you use two SZ100 as a cluster to manage upto 2048 APs and one of the SZ100 goes down, then only 1024 APs will be managed and rest of the APs will be disconnected from cluster. You should consider SZ100x3 node cluster, if you want to manage up-to 2048 APs with active redundancy.
Alternate and better option is use "virtualSmartZone - High scale", as single vSZ-H node can manage upto 10000 APs (with maximum hardware resource level).
I wasn't aware of that possibility. AFAIK in order for a SZ-100 to handle more than 1024 APs a 3-node cluster would be required, because having only a two node cluster only 1024 APs would be supported. So is there a way to have only a 2-node cluster and support 2048 APs?
Yes, if you have 2 SZ-100 in a cluster, you can manage upto 2048 APs. But As Syamantak mentioned above, if one SZ goes down then it cannot maintain 2048 APs. 1024 APs will be managed and rest of the APs will be disconnected from cluster.