for the s13 sr20det motor, will it make a difference in performance and/or sound of the BOV if it gets placed on the throttle body side or the turbo side?

The BOV or CBV should be placed as close to the TB as possible, since there is differencial across the midpipe, especially if you have an FMIC. In other words, the pressure at the TB is different from the pressure at the compressor outlet, which is different from the pressure at the FMIC's inlet and outlet. Sometimes these numbers aren't very different, but the only number that matters is the one at the TB, so the release needs to be there. Get it?

Im not sure if your statement was an opinion or fact but all JDM BOV kits have the BOV placed on the turbo side for the S13. Even the factory bov for the S13 is on the turbo side unlike most other applications(7m or 2jz) where it normally is on the TB side. I dont know why but maybe for venting reason; as a hose from TB side back to the intake tract would be too long????/

Beats the crap out of me, but I state facts. I tend to agree with your statement about packaging, if not path lengths. I don't really see why something like the GReddy kit wouldn't put the BOV up next to the TB, though, as that pipe is big and straight; perfect in my book.

They probably place them there for other reasons as well. They build huge restrictive air boxes to reduce engine noise. The BOV, could also be noisy if mounted closer to the firewall, right near the TB. Manufacturers like to make things all frilly for the 90% of the car buying world that care more about a quiet ride than maximum performance.