@StonedEdge With an aggressive overclock (e.g. 2300MHz/900MHz+) some 3DS games are playable on the Pi4, mostly RPGs. In addition to that you will need to optimize every setting possible as well as make use of any possible cheats that can speed up gameplay. For example, the 150% speedhack in Pokemon Sun is enough to get the game playable on my Pi4, which was a pleasant surprise. Less demanding RPG's like Etrian Mystery Dungeon, Etrian Odyssey, Pokemon Mystery Dungeon, Pokemon ORAS all seem to be playable even if they are not quite at full speed. That said, games like Mario Kart and Smash Bros are just out of the question as really any slow-down is completely unforgiving in games like these. If your interest is mainly RPG's and you are comfortable with overclocking, then I would say that it might be worth it for you to get Borked3DS working on your Pi4.
That said, I believe that the bigger motivation for you to make the jump to 64-bit should be for Gamecube emulation as that is lower hanging fruit than 3ds. Gamecube emulation is a measurably less demanding than 3DS in large part because dolphin has the CPU override feature that works far better than it does in Borked3DS to speed up games on slow hardware (honestly, dolphin is just a better piece of software than citra was and it has far better optimization for use on a variety of devices).