Around about 2010 (I think) there were problems with some new PS11s having a strong odour - I should know because I bought one of them from Net-a-porter. It was my second PS11 and the first one had no smell other than the usual lovely new leather smell. PS were very evasive about it but it seemed they were using a particular oil to treat or seal the leather at the end of production. Anyway the smell faded after a while with no lingering after effects at all and I still use that PS11 regularly. I've bought 4 other PS11s since then and none have had any weird odours so it was a very short lived production issue.
As for the weight of the bag, I usually carry Classics and I find them lightweight as well as very tough and sturdy. It may be that the hardware on the Minis make them a little heavier than other bags of a similar size. PS have been busy stripping hardware from the PS11s so weight issues are more likely with older season bags.
Good luck with your purchase