Welcome to the forum! 
I take it you mean you edited /etc/fstab. fsck is a command for checking and/or repairing a filesystem.
By not using any configurations from Mint. You said yourself that you are mounting a Mint home directory. This means that Manjaro will apply as much of that configuration as is already defined in the preexisting configuration files, and it will use the upstream defaults for things that were not yet defined in there — e.g. the wallpaper with the mouse.
By not mounting the same /home in both distributions. You have to give each of them their own /home.
What you can do in order to have your data shared between both distribution is put that data on a separate partition that you then mount to a directory inside your $HOME in either distribution, or with another mountpoint — e.g. under /mnt — that you then create a symbolic link for in either $HOME. For instance, you could make ~/Documents into a symbolic link, instead of having it be an actual directory.
See if this tutorial below can provide you with inspiration. 