There is nothing wrong with using porcelain tiles, just the fact that you may have wanted to lay without/minmal grout joint. Even if the tiles are rectified, they will still not be EXACTLY the same size, don't be fooled into thinking they would be.
PVA has no place in a tiling installation. Tiling straight onto chipboard can be done with appropriate adhesives, but it is much better to prepare the floor by over boarding first. Depending on the adhesive you choose to fix the tiles with would depend on wheather the floor would need priming or not. BAL for instance stipulate sealing the back and edges of ply before laying with BAL Bond SBR and NO primer on the tiling surface. Ardex on the other hand, say to seal back and sided with polyuerthane varnish and prime tiling surface with P51 primer.
What ever you choose, check the manufacturers recommndations carefully.
1 last thing, if you go for a 1mm grout joint, it is very easy to lose it because of variances in tiles sizes as stated before.