Many consider 7* max, with no more than 1 difference. You also don't want the angle to be 0. It needs some to move the grease around in the bearing cups.
https://4xshaft.com/blogs/general-tech-info-articles/driveshaft-angles?srsltid=AfmBOoqXyj07kBD8fEpqTlkK_MXBjefyHMnsCIqclUCKzsUSOJSwiOTI