A list of states that have additional requirements for Excelsior graduates is listed here:
State Board Requirements - excelsior.edu
Like geminiLPN-RN confirmed, Mississippi is not one of the states that has additional experience requirements, etc.
As for the program itself:
Just go through Excelsior on your own without any third-party involvement and you should do just fine both academically and financially. There's a thread on the College Network, which applies to other non-affiliated third party networks here: The college network
Bottom line... you don't need (or necessarily want) to involve yourself with these third parties.
I am nearly finished with my Excelsior program... CPNE in mid-September. I know you're in a hurry to earn your RN, but please keep in mind there is a LOT of studying and time commitments ahead of you. The FCCA (a course that follows completion of all of your nursing core classes and precedes the clinical examination [CPNE]) is not self-paced anymore; it'll require 8 weeks of time on its own. The CPNE has a minimum of a 2 month wait to your test date from the time your CPNE application has been completed. You cannot apply for the CPNE until your nursing core courses have been completed, the FCCA has been passed, and you are no more than 10 general education units away from completion of the entire AS or AAS program.
This journey will end nearly at the two year mark for me, assuming I pass the CPNE the first time around (fingers crossed). There's been a lot of textbook studying and a lot of work on my own to become proficient in the nursing skills that differ from my paramedic ones. I have no regrets at all, and learned so much from this experience. You need to be VERY motivated to work on completing this program on your own; you will have days where you just want to yank all your hair out from the studying, lol! If you live with family, they have to understand that oftentimes, you simply do not exist in their world. This is particularly true when studying for the CPNE, which is an exam of near-perfection and nerves, where you are assigned the nursing care and documentation of patients you've never met before at a hospital you may have never stepped foot into.
Just wanted to give you a "heads up" on what to expect; not trying to scare you off. I know in the past, Excelsior was able to be completed in a very short period of time; I know of an RN from my area who finished it in 101 days, but that was many years ago. That's no longer the case; the bar has been raised (which is good IMHO).
Good luck to you in whatever decision you choose!