I asked Jio Fiber office in my location. They don't have any information regarding Dynamic IP address nor private for that matter.Jio FTTH is not for advanced users who like to do port forwarding or any advanced router functions like run custom scripts. If BSNL is not using CG-NAT, just stick to it. Ideally, most ISPs worldwide, put you back on Dynamic IP address if you make a formal written or email request asking. You just have to mention them a valid reason like access to remote desktop or home CCTV cameras for security.
It wouldn't really introduce any significant additional latency, maybe a millisecond or two max.
For normal web related activities, it should work alright.
Also, unless you have a lot of client devices, the load balancing may not be that effective.
I do use Jio 4G as a backup WAN, BSNL being the primary. Been working great for a while now.