The Open Source Cartridge Reader is a great diy project for dumping your own roms and saves. If you order a kit with the surface mount components already installed, it's also a great beginner soldering project.
The closest thing I ever used that backed up actual hardware was a Playstation 1 card reader. At the time I was backing up game saves and porting them to the ps2 for emulation or something i forget exactly.
It was wild to do something like that on your computer back then. A Sony memory card in your PC? Bonkers.
I built one of these a couple weekends back and have been blissfully extracting ROMs from my cartridge collection since then. I love it so much, and it's a really solid design!
The retrode was a good device when you could buy it. What I like about this one is that you can dump all the popular cart systems without needing adapters, while being able to build additional adapters for less common systems.
Hmmm, I still have my N64, all my old games, etc and could test. Do you know if there is a way for me to check the memorypak to see what games actually saved to it?
Now that you mention it, I recall either OoT or MM saving to the cart directly.
Edit: May have found my own answer:
HOLD THE START BUTTON DOWN and turn your console on. Make sure to HOLD THE START BUTTON DOWN while it boots up. This will pull up the data management screen where you can view and delete your stored data on your memory card.
IIRC none of the games that require the expanded RAM module (DK64, OOT, Majora) actually utilize its RAM under normal conditions. For instance, DK64 only used it as a means to stave off a memory leak.