rxTools (especially 2.6) is outdated. I can't list what it lacks compared to Luma for example, but if you never felt like something was missing, you probably don't need to update, even though it's better to use something that is still maintained.
If you are not even aware of menuhax, that's an entrypoint that loads automatically at the end of sysNAND booting and allows you to autoboot to your CFW for example.
arm9loaderhax is the newest entrypoint to boot your CFW and other stuff. It has a boot rate of 100% and is so fast you can't even tell the difference with an unhacked 3DS. It runs before sysNAND, unlike menuhax.
It also allows (but does not force you in anyway) to ditch your emuNAND and do everything on sysNAND.
Other stuff that ends in "hax" is an homebrew entrypoint like menuhax, but less convenient
Freakyhax for example is a hack based on Freakyforms Deluxe, which allows you to get to the homebrew menu... Which you can already do using the HBL cia mentioned by
@Ella879 so you don't really have to worry about that. And getting to the homebrew menu allows you to play Minicraft for example, or run anyother homebrew you may like.