Now I'm not sure how they react with a laser but RC-3 does let off a slight smell when being cut (with a cutting disc) for quite a long while due to it getting very hot and I never noticed if the Clears do the same. But if you're going to be cutting it, you would be better off making a mold and making it the shape you need from the get-go and not having to cut it at all. Or if you really want to do cuts on the resin, then a Dremel and a cutting disc would be a lot better idea than a laser.
I had to look up laser cutting to understand a little bit of how it's done and from what I've seen - I REALLY would NOT recommend it as you are essentially "melting" the resin when you cut it with a laser and that is NOT a recommended thing to do. The resin does give off fumes when melted (never tested the melting itself personally but have seen it give off slight fumes when having to bake Sculpty on a resin piece) so I personally would not do laser cutting on any resin.
For the mold material itself, I'd go with a tin cure silicone like one of the HS series and for what the mold is copying - the sky is the limit, silicone won't stick to anything except silicone and it won't hurt 99.999999% of materials it is cured against. I've made molds of things from gummies to plastic toys with stickers on them and when I need finer details to show up, HS-3 picks up the tiniest details.