Haven’t disassembled my Hero Box down to MB to check internal SSD mount, but should be 22mm socket.
Existing drive identifies as Intel SSD SCKKF180H6 which lists as a M2 2280 TLC module using SATA 3 interface. It should be possible to replace with a larger capacity M2 up to 2280 length.
Crystal DiskMark yields average reads for a TLC drive, but a little slow on writes.
There are some settings in the Hero Box BIOS referring to NVME drives and the N4100 CPU is capable of NVME/PCIe, but only way to know for sure ChuWI implemented it is to try one.
There is a bay on bottom to take a SATA 3 SSD or HDD. I installed a Samsung EVO 1TB SSD, but with extended video watching (2+ hours of HD playback), the Hero Box CPU temps went too high. Even had a couple thermal shutdowns. Turns out the hottest area of the motherboard is directly above the SSD area and the warm SSD covering that area locks the CPU heat in. The “Silent” passive cooling thru tiny openings around the top and bottom is just not up to it.
Micro SD slot is not worth the bother. It’s down in a recess in the faceplate and hard to pull out without tweezers. Also very slow transfers. Using a SDXC Class 10 chip in my other computer transfers of 3GB of files are steady 90-95 Mb/s. In the Hero Box, same Class 10 chip barely reaches 25 Mb/s copying to the 180GB drive - often dropping below 10 Mb/s