Using single vlan vs multiple vlan. Objects deployment wizard gives you the option to select separate VLAN for Client Access Network and Internal Access Network.
Objects deploys one to many load balancers which gives you protection against node failures, if any S3 endpoint goes down, you will always have other endpoints to reach your Objects cluster. You can access Objects S3 endpoint from any client access IP shown in Objects UI against Objects instance..
Networking requirement is pretty simple for Objects but when it comes to fine tuning network for your new production deployment, there are few aspects we can consider.