This is a super common question, and the answer is of course... It depends...
For home, we would typically recommend a small or medium size sign. Our signs are very bright so you don't need a huge one to create a really nice neon vibe. It's easy to get carried away and think "my living room wall is 3 meter wide, so I want a 3 meter wide sign" but in reality that will be too big and a 1 meter sign will be plenty.
For commercial spaces, it depends on the size of space. For a selfie wall, medium is a good size, but if you are creating a phrase, split the worlds over multiple lines so it stays more of s square shape. This is so its easy to get the whole sign in the photo.
If you have a large feature wall, or event space, we have made huge 5-6 meter wide signs and have plenty of photos. It's best to get in touch with us at firstname.lastname@example.org to discuss your exact requirements.
As always if any one needs help, or wants to know the exact size their sign will be. Just contact us and we will happily help :)