Yes & no
Condition of paint varies between batches, what it's designed to do, how it's been stored etc, guns may be picky about paint - historically 'woodland' guns are hard on paint and expect a 'tough' paintball that can cope with rough handling and 'speedball' guns are gentle on paint expecting it to be very fragile to pretty much guarantee a break on the slightest impact
Precise sizes will also vary between batches and vary during the day depending on the atmosphere and whether the bag has remained sealed from moisture
You can buy paint in various grades, the lowest being training or punter paint, the 'best' being tournament paint, but that is too simple to make it the best for the day and your gun
The thing is will this matter to you - a ball that is size matched to your barrel bore can grant you the most efficiency, and consistency - as long as the rest of the bag is consistent with the ones you checked. If you can carry the paint you need and have the air capacity to shoot it at the required velocity then your efficiency is sufficient, and if you can reasonably predict the direction and range your paint will fly then you have sufficient consistency
