Both of your questions, LED and dual battery, are heavily discussed on this forum. Searches for 'LED' and 'dual battery' will give you at least a few days of reading. Popular discussions trust me
But for your first question, many on this site have replaced their 921's with LED's. Again, a popular search topic. All kinds of info.
And almost everyone wants a dual battery for more 'dry time' camping. Lots of good ideas here. And again, another very popular search topic.
I know you will find what you are looking for. I'm new on the site as well and welcome.