Our 3D Printers are pretty nice. Especially with PLA, your first layers should be smooth and precise. You shouldn’t get any texture or transparency. If you do, it is very likely that the z-height is misadjusted.
I’ve added some pictures to the wiki here: Prusa MK3S+ - Asmbly Wiki
Why does this happen? The z-height adjustment does drift a little over time, but it’s also possible that someone recently printed with a different build plate and adjusted the z-height to match, or was doing a specialized print that needed an adjustment.