The brand is written using some decorations. Should I register the brand as a word trademark or a logo trademark?

In general, you have three options.

1. You can consider registering the brand name as plain text (wordmark) if the design elements are not distinctive. In this case, the text will gain 100% protection. If a third party uses the wordmark in the area of your sales with any font, it would be considered trademark infringement. Since you have ownership over the words, you can stop the third party from using them.
2. If the decorative elements used with the text are integral to your brand identity, it would be a good idea to register them together with the text. In this case, you would need to submit a logo trademark. This way, you would get some level of protection for the decorations and the text. However, the level of protection depends on how dominant the decorations are. The more dominant the element, the higher the protection.
3. You can register both the wordmark and the logo (including both the text and the decorations). This way, you can gain the broadest protection. However, you will have to file two separate applications and pay double the fees.