[quote="ZophiasDad, post:1, topic:22679"]1. does your installer allow you to manually set up your HD's?[/quote]...been answered - yes.
[quote="ZophiasDad, post:1, topic:22679"] If so what partitioning tool is used? [/quote]I believe
parted(libparted) is backend which it accesses via use of KPMcore. The front-end is from the installer design ...so not same as one might have seen before; similar of course to all such tools but unique to Calamares. It is pretty basic; not as robust as KPM(KDE Partition Mangler) or GParted.
[quote="ZophiasDad, post:1, topic:22679"]If you have your HD pre configured does the installer allow you to use your setup or do you need to do this inside the installer?[/quote]That's kinda loaded. The installer uses your setup meaning that it reads all connected disk drives and presents the list with a default install selection that it guesses is where one wants to install Manjaro.
The guess is almost always wrong of course, unless you are using a blank drive then it is always correct, . That is the state of all partitioning tools; none I know of have learned to read mind of the $USER.
So one must normally tell it which partition to use or create a new partition and tell it to use it for the ML install.
Whether new partition or reusing a current partition, the chosen partition(s) must have a filesystem(fs) installed and then formatted.
ALL data will be irrevocably* lost on that partition when it is formatted.
Note that unlike some other OS, Linux can be installed on any primary or logical partition; i.e., it does not have to be a primary partition.
In addition one must specify where the bootloader gets installed as it always gets that wrong too. There is a list of choices so choose the correct one for one's desired setup.
Normally one wants it on the same drive (not partition) MBR where ML will be installed but there are valid reasons for choosing install to root partition or even some other partition or drive.
One needs to be careful. If one tells it to format and install to a partition it will do it. Choose unwisely and one could easily format over data one wants to keep. ...
If there are any doubts or special needs for the partitioning then perform it using a familiar tool, before beginning the install process. During the install just point Calamares to the desired pre-formatted/setup partition during that phase of the install. Also check that the bootloader will be installed to desired location.
Calamares makes the installation of Arch/Manjaro Linux pretty easy. One just needs to pay attention and check actions before clicking that mouse button to perform the function.
*irrevocably => not quite. These days with enough luck, time and money the data can almost always be retrieved from partitions that have been simply formatted. Fully formatted and/or written-over parttions present more of challenge so require more luck, money and time to piece it together.