You can replace tag.png with tag.max.png in the URL to get the largest tag size.
GBAtemp has a different code for the tag because it cannot dynamically update in the signature. You can also share your tag with your friends on Discord by using the !riitag command using RiiConnect24 Bot.
Viper has 4 coins. Every time you play a game when you have RiiTag connected to your console, you get a coin!