Ah okay, that's what you meant. You can't download updates
with the multi-launcher, but you can download them from the eShop and use them with roms. Basically it's just a UI for picking the rom you want to load. The only other reason to get a Gateway is to use it's Gateshark Cheats.
And to reiterate on what
@Quantumcat was saying, the multi-launcher is only available in Gateway mode. And it's kind of a crutch that breaks updates constantly for them. That and their obfuscated messy code. Gateway mode has other crutches like not being able to run DSiware or GBA games and it's missing sigpatches in some places, causing stupid issues.
You should know that your CFWs are out of date, and that there's no reason to use ReiNAND and AuReiNAND at the same time really. Additionally, AuReiNAND was rebranded when it updated a while ago to Luma 3DS, and you really should be running that more recent version. Luma3DS also has homebrews you can install to the home menu that update your CFW with the click of a button.
Gateway is basically a fancy CFW with enhanced Flash Cart functionality, though most of us do not support them anymore because they are an incredibly shady business. They heavily obfuscate their code, and it even has hardcore brick code in it, where if it detects if you are using any kind of clone of the Gateway, it bricks you so hard you get a Bootrom error. More recently they ripped off open source code and exploits and removed all the safety precautions involved in setting up Arm9LoaderHax and caused quite a stir in this community, and it's not the first time, and probably not the last time they pull stuff like this.
Typically the most ideal setup for a 3DS is Arm9LoaderHax booting into Luma3DS CFW SysNAND and having all games installed to the SD card from CIAs or though things like freeShop. The reason everyone is switching to Arm9LoaderHax is because it runs before the 3DS's OS does instantly without failure, even on reboots into DS or GBA mode. So it works as brick protection and nullifies the need for an EmuNAND, plus, Luma3DS prevents Nintendo's Updater from removing Arm9LoaderHax from the system, meaning it is essentially a perfect, self sustaining entrypoint and CFW, never have to worry about your SysNAND being updated, because you're free to update as you please, and still have all the benefits that Luma3DS provides.
The guide I linked above provides rather simple instructions toward the end on transferring your EmuNAND to your SysNAND and removing the EmuNAND from your SD card, so you won't lose anything, and you'll gain some space back on your SD Card.
Ideally, you'd simply get a large SD card for your 3DS itself, and then install all your games to the Home Menu directly, instead of having to fumble around with buttons on a cart or clunky rom selection menus, or worry about headers or any of that. Plus it frees up your 3DS's Card Slot to use an old DS flashcart if you have one, so you can play DS games too.