why is this so confusing? Oh, b/c free usually means 'you have to work for it'

ok.... I called chase- and asked about closing date- which is March 23- she said the points likely wouldn't post till April 23 (bleh!

) I have some questions-
What does the 'switchover' mean? I applied and got cards before the switch date- but I am totally confused- I was promised 2 free R/T for using the card-
Do any changes impact my choices of flights? Do flight prices change seat choices? Are these free tix- limited? The old way,vs the new way?
I had thought when i signed up, when the tix were awarded, it isn't contigent on the flight prices- am I wrong?
(asking b/c I have to wait for rewards to post,and I see flights for my dates now,that are pretty decent prices,so i'm felling anxious....)
The good part is we don't travel till next fall, but prices have me concerned that waiting for points to post might lose me the flights I need,if there are restrictions.....