I’ve read some posts about editing fstab to mount them at startup, but they don’t cover whether the drives will be available to other users or not. Can I just add them to fstab and mount them somewhere that’s available to all users, then sort out the permissions? If so, where’s the best place to put them?
Yes pretty much. It just explicitly tells the system where to mount it, and for some filesystems you can even force the UID/GID and modes.
Usually /mnt/whatever for static mounts and /media/whatever for removable mounts (those appear as drives in file managers, whereas /mnt doesn’t). You can set the users option in fstab and it’ll let users mount and unmount it without sudo as well, or auto to always mount it on boot.
From there usually you can make a shared group, chown the mount to root:thatgroup, then chmod g+s to make sure the group is inherited. And you should mostly be good to go.