Usually “standard” Irish refers to the Caighdeán Oifigiúil. It’s a kind of Irish that was designed for official use on government documents, radio and television, etc. and is a kind of “middle ground” between the major dialects. It’s more than just spelling – it affects the grammar and lexicon as well. The “authentic” dialects like Munster, Connacht, Ulster, are much more than just spelling differences. A book can be written in Munster Irish and be spelled however the author or the editor choose. It doesn’t change that the grammatical features and word usage are Munster. As an Irish learner you’ll be forced to be somewhat adaptable to spelling, as there is a lot of variation. As the poster above says, you have to learn to concentrate on sound and let that guide your understanding of what you’re seeing in print, and not the other way around.