Consider whether you want just Chinese numerals, or also Arabic (normal) numerals in the corner.

Consider which style of mahjong it will be used for. Depending on the style, there are different numbers of total tiles included in the set.

The feel of the tiles might matter to you, but unfortunately that may be difficult to judge when buying online.

Have you imported the tails-signing.key yet? Usually you can double-click on that to import it using whatever graphical gpg frontend is set up on your system. It may ask you how well you trust the owner of the key. You can answer that question however you want without affecting this verification process.

Next, it looks like you run the instructions from this page: https://tails.net/install/expert/index.en.html#verify

Some of those command line parameters look a little paranoid. The basic command you want to run is: gpg --verify somefile.sig somefile.img

NTFS is considered pretty stable on Linux now. It should be safe to use indefinitely.

If you’re worried about the lack of Unix-style permissions and attributes in NTFS, then getting BTRFS or ext4 on Windows may be a good choice. Note that BTRFS is much more complicated than ext4, so ext4 may have better compatibility and lower risk of corruption. I used ext3 on Windows in 2007 and it was very reliable; ext4 today is very similar to ext3 from those days.

The absolute best compatibility would come from using a filesystem natively supported by both operating systems, developed without reverse engineering. That leaves only vfat (aka FAT32) and exfat. Both lack Unix-style permissions and attributes.

The existence of one or more gods can’t be conclusively proven or disproven. So it makes sense to me that some people believe in it and others don’t.