Unless Libreboot has peculiarities I am not aware of, you can partition the
disk the way you want. Does the disk have an MBR limited to four primary
partitions? Even if it does, one of them can be an extended partition that
can contain as many logical partitions as you want. A logical partition is
neither worse nor better than a primary partition and, contrary to older
Windows, any part of GNU/Linux's file hierarchy can be on any partition type.
It really does matter.
Contiguous data at the end of a HDD are supposed to be more rapidly read
because the disk has to spin less... but, whatever the position of a
partition, you will probably never feel any difference in a desktop usage. An
SDD does not actually have a beginning and an end because it does not have
disks.
As for the choice of the partitions, their sizes (including that of a swap
partition) and their filesystems, read this old thread for rather advanced
advices: https://trisquel.info/forum/full-disk-encryption-multiple-partitions
What has mainly changed, since 2012, is that Btrfs has matured and, even
though it still cannot be considered as stable as ext4 or XFS, one should not
be too afraid of losing data in it.
In summary: do not worry and if you do not want to spend time studying all
that, choose the default partitioning. It is OK and, talking about a desktop
usage, there is almost no performance gain to be expected out of all that.
