Hmm, it's difficult to tell without pictures. I don't buy my jeans tight, but over the first 2-3 weeks they normally stretch without much pressure. Still, the main characteristics like thigh measurements will stay the same. so make sure you really want to go with that size, otherwise try to return or resell it. Regarding the hemming - I would wait approx. 1 month until the combs have settled, as this reduces the effective length of the jeans. Don't cut off too much at once, rather small steps. A hot wash will cost you around 0,5" on top.