Those bearings are good and using spacers is good in theory but I feel like it depends on if the space inside of a certain wheel matches with the length of the spacers that are being used. The length for both varies a lot, so sometimes if you have a situation where the spacer is too long compared to the wheel it could actually damage the bearings. I've actually had this happen before in the past and fucked up my bearings pretty badly.
The dude in this vid does a good job explaining it, starts at around 0:40