I have a vague memory, but can't have been as small as yesterday's. That was like a Sunday amateur pitch (for size),
IIRC, at the time, it was the narrowest pitch in the league. I think the length has to be standard for all pitches, but the width can vary.
Though, none of that helps Arsenal who've played on a much wider pitch since 2006. So playing on a ground like Bournemouth's can't be easy.
Also, the "advantage" of narrow pitches is that they're specifically designed around the confines of the stadium, so the stands are almost literally on the touchlines. Can be quite intimidating for visiting teams, and a boost for the home side. When Wenger helped design the Emirates, he wanted to retain that. I've been to both grounds, and can confirm he didn't quite achieve it.