Likitha patam (written formats) is not permitted as per Panini’s siksha. Siksha is a text that prescribes how to learn, and the intonations involved; as it has stated it should not be in written formats, it is better not to refer to texts while reciting and it has to be recited by heart as per the religious norm. Doing so is a dharma on its own.
The important aspect is, that this should be learned from a Guru and not by reading from a book. If one cannot recite it by heart, it is not wrong to refer to the book, but it is important to note that one must have learned it before from a Guru.
Swami Desikan has mentioned in Sri Pancharathra Rakshai that it is better to chant Veda during the Svadhyaya period. The Svadhyaya period is when one takes a rest after partaking food. During that period, one can meaningfully pass time by doing parayanam of Stotram, Divya Prabandham, and Srimad Ramayanam. Doing Veda Parayanam is considered special during that time, states Swami Desikan. It does not imply reciting other stotras is considered a sin, instead we should not neglect the Vedas. But chanting Veda is considered supreme, and Swami has indicated which part of Veda is to be chanted as well.