An interview said basically nothing story-wise has changed. Apparently no new dialogue recorded, no codex changes, etc. The only real difference mentioned would be that the Extended Cut ending for 3 would be the default.
Makes sense, since bringing back voice actors a decade later would carry quite the price tag.
1’s combat is supposed to get tweaked to slightly make it more in line with the sequels though.
Derpibooru costs over $25 a day to operate - help support us financially!