If I follow all the steps for the CFW video, will I be good?
I'd say a9lh is a tad overrated as someone who just did it on one of my consoles. Scary potential system brick opportunities during the long setup and all you really gain is a slightly faster bootup time that works 100% of the time instead of 90% of the time. You also attain some anti-brick support via being able to boot directly into decrypt9 and potentially reflash an older version of your sysnand if you brick it.
BUT you lose out on region free(none of the a9lh cfw's currently support it), which I personally think is a pretty big loss but people like to defend a9lh on that front because it will likely be supported in the near future and a lot of region locked games can 'be found' region unlocked.
Other than the initial cool factor of being able to turn on the system and have it work just like an unhacked 3ds, there isn't much to a9lh for the layman user. rxtools is easier to setup, minimal risks assuming you've already downgraded and will provide you with all the functionality you could want for the most part. If you can live with the slower boot time and the once in a blue moon hang on startup, I'd skip a9lh. Just my personal opinion as someone using both, but hey, who knows, maybe there are some cool features I am unaware of that a9lh provides to power users.