When it comes to the NES, what exactly is the difference between

>>3876280
>Or is it a 1:1 experience and all you're missing is the je ne sais quoi of having the original cartridge?
This. It's about the same as bootleg carts, except you can write your own games on it.

>>3876280
As longs as the FPGA implementation of the mapper used for the loaded ROM is a faithful recreation of the original,
which on both the Powerpak and N8 most of the mappers existing already are, you won't be able to tell the any kind of difference in how they behave.

I don't think anyone can tell the difference.

I wonder if it's possible to rewrite your own ROMs on one for
150 in 1 flashcarts. Anybody know?

I don't know if shit like battery backed saves would work but otherwise it'd be like any of the multi-game carts you could buy