Which FS format should I use?

sry I had to remove my other post cuz of my security keys were exposed. Follow my layout and you will never need to worry about space, I promise U this.

Migrating your core system to an SSD while using your HDD for large directories via bind mounts is the best way to get maximum SSD speed without running out of space.
Here is a live example of how a production Linux setup structures this using dedicated fast drives for OS paths and bind mounts for storage:
1. Core Operating System on SSDs / NVMe
Instead of putting everything on one drive, you put the speed-critical mount points on your high-speed SSDs:
/ (Root): Placed on fast NVMe (/dev/nvme1n1p3).
/boot/efi & Swap: Placed on fast NVMe for instant boot/wake times.
/home: Placed on a secondary SSD (/dev/nvme0n1p1) so application configs load instantly.
/usr & /var: Can even be isolated on their own SSDs (/dev/sdf1 and /dev/sdg1) for heavy binary loading and rapid log writing.
2. Using Bind Mounts for Heavy HDD Storage
Rather than filling up your fast /home drive with big downloads or media, you mount a large HDD (e.g. /dev/sda1) to a base location like /mnt/ironwolf and then bind mount the heavy folders directly into your user home folder.
In /etc/fstab, it looks like this:# 1. Mount the main HDD partition
UUID=b9877b57-3190-4ba6-b12c-dbddb90290cd /mnt/ironwolf ext4 defaults 0 2

Bind mount HDD subdirectories directly into your home folder
/mnt/ironwolf/Downloads /home/username/Downloads none bind 0 0
/mnt/ironwolf/Documents /home/username/Documents none bind 0 0
/mnt/ironwolf/Pictures /home/username/Pictures none bind 0 0
/mnt/ironwolf/Archive /home/username/Archive none bind 0 0

Why Bind Mounts Beat Standard Symlinks Here:

System Integration: Applications treat bind-mounted directories as real, native local folders rather than shortcuts or soft links. Permission Control: Keeps standard file permissions intact seamlessly across the system. Clean Home Directory: Your fast SSD handles hidden config files (.config, .local), while the big HDD handles heavy file storage transparently.

/etc/fstab: static file system information.
Sanitized configuration template based on a multi-drive system layout.

PRIMARY SYSTEM DRIVE (Samsung 960 EVO - NVMe 1)

/ (Root)
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX / ext4 errors=remount-ro 0 1

/boot/efi (UEFI System Partition)
UUID=XXXX-XXXX /boot/efi vfat umask=0077 0 2

High-Speed Swap
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX none swap sw 0 0

DEDICATED SSD OS PATHS

/home (Intel NVMe 0)
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX /home ext4 defaults 0 2

/usr (Kingston SSD)
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX /usr ext4 defaults 0 2

/var (WD Blue SSD)
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX /var ext4 defaults 0 2

HEAVY STORAGE & BIND MOUNTS (Seagate IronWolf 3.6T HDD)

Primary HDD Mount Point
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX /mnt/ironwolf ext4 defaults 0 2

Bind mounts into Home Directory
/mnt/ironwolf/Desktop /home/twzzler/Desktop none bind 0 0
/mnt/ironwolf/Documents /home/twzzler/Documents none bind 0 0
/mnt/ironwolf/Downloads /home/twzzler/Downloads none bind 0 0
/mnt/ironwolf/Music /home/twzzler/Music none bind 0 0
/mnt/ironwolf/Pictures /home/twzzler/Pictures none bind 0 0
/mnt/ironwolf/Archive /home/twzzler/Archive none bind 0 0
/mnt/ironwolf/Full_Archive /home/twzzler/Full_Archive none bind 0 0

UTILITY & BACKUP DRIVES (Optional / As Needed)

Timeshift Snapshots Drive (WD 1TB)
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX /run/timeshift/backup ext4 defaults 0 2

Secondary Backup Drive (Hitachi 1TB)
UUID=XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX /mnt/backup ext4 defaults 0 2