It is unrealistic to ask a question like “Is that normal?” – it simply cannot be answered with any authority.
The relative size of an ISO file will vary across Editions and/or Distributions, dependent upon the content it contains, its purpose, and the intended audience.
Suffice to say ISO’s are typically not getting any smaller for any OS; whether it might be any of the distributions you mentioned, Manjaro, BSD, MacOS or Windows.
Step 1. Download the ISO – Manjaro Downloads – Download the full ISO rather than minimal (personal recommendation).
Note that it is also possible to download an ISO via Torrent (a bit-torrent client is required).
Step 2. Verify the ISO against the provided checksum (SHA256) – See the More button of your chosen OS download.
In KDE Plasma: right-click an ISO, select Properties → Checksums and validate the checksum via that dialog.
A worthwhile alternative to writing the ISO content directly to USB is to create a Ventoy USB instead:
Ventoy
Boot with a Ventoy USB, and ISO files are automatically listed in the Ventoy menu, and can be booted directly. A 32GB capacity USB should allow ample space to store several ISOs of your choice; an 8GB capacity USB might hold one, or two ISO’s; do the math.
Ventoy is available from the official Manjaro extra repository:
sudo pacman -S ventoy
Write the Ventoy system to an empty USB drive;
- target the device itself
/dev/sdX, and not a partition
Create a Ventoy USB (for UEFI mode): 
sudo sh ventoy -i -r 100 -S -g -L VOLUME /dev/sdX
Create a Ventoy USB (for BIOS mode):
sudo sh ventoy -i -r 100 -S -L VOLUME /dev/sdX
- Enable
-s or disable -S Secure Boot.
- Substitute
VOLUME for a volume label name to use.
- Substitute
/dev/sdX for the location of your USB device.
- Preserve some space on the target device (example allows 100mb).
Ventoy general usage
Type ventoy (without arguments) to see usage information:
Usage: Ventoy2Disk.sh CMD [ OPTION ] /dev/sdX
CMD:
-i install Ventoy to sdX (fails if disk already installed with Ventoy)
-I force install Ventoy to sdX (no matter if installed or not)
-u update Ventoy in sdX
-l list Ventoy information in sdX
OPTION: (optional)
-r SIZE_MB preserve some space at the bottom of the disk (only for install)
-s/-S enable/disable secure boot support (default is enabled)
-g use GPT partition style, default is MBR (only for install)
-L Label of the 1st exfat partition (default is Ventoy)
-n try non-destructive installation (only for install)
Update a Ventoy USB:
- ensure the updated Ventoy version is available in Manjaro; and then:
To update the Ventoy system on an existing Ventoy USB;
sudo ventoy -u /dev/sdX
- The Ventoy USB update process is non-destructive.
See also: Ventoy (GitHub);
Notes
-
There is a Windows GUI version of Ventoy. If you choose to use it please pay attention to available options in the File menu before creating the Ventoy USB.
See also: Ventoy (GitHub);
-
This is noted (somewhere) in Ventoy’s own documentation, but I’ll add it here for convenience; When an ISO is dragged/copied to the Ventoy USB it’s recommended to rename the ISO (using underscores) so that no blank spaces appear in the filename.
Welcome to the Manjaro community.
As a new forum user, please take some time to familiarise yourself with Forum requirements; in particular, the many ways to use the forum to your benefit:
Required Reading:
Resources:
Update Announcements:
The Update Announcements contain update related information and a Known Issues and Solutions section that should generally be checked before posting a request for support.
System Information:
Output of the following command (formatted according to forum requirements) may be useful for those wishing to help:
inxi --admin --verbosity=8 --filter --no-host --width
Be prepared to provide more information and outputs from other commands when asked.
Regards.
