Great looking figures Rob, and if you don't work with plastic often, Plastic Soldier Company is a good starting point. They are both cheap and relatively nice for the price (depending on which set, some of the old ones are not great, but the new ones are really nice). The detail is also softer on most plastics since they have to worry more about undercuts when working with the metal injection molds required compared to silicone molds for metals. You just have to paint them slightly differently than metal figures. As for weight, yeah it takes a while to get used to, but one HUGE benefit is that if they get bumped or dropped they normally don't break, and you can say goodbye to chipping! That is the biggest thing that makes me far prefer plastic over metal, all my metal figs end up chipping no matter how careful I am.
Anyway, enough babble.... I think these look really good, so I wouldn't change anything too much. If you're worried about the faces, just give them a dark wash and then pick out the highlights again. I look forward to your terrain piece coming up before the end of the challenge.