Considering what I already have painted, which 3 mechs should I paint next to fill out the two Mech stars? Here's what I have available:
My thoughts are maybe the Dire Wolf and Warhammer (as one of the canon Clan refits) to finish off the heavier star as an Assault Star? Then I',m thinking the Vapor Eagle to run the lighter mechs as a Striker Star? What do y'all think?
That could work.
It looks more like a Cavalry Binary to me, so while the Dire Wolf is a great anchor, it is an expensive and slow one. Definitely go with a Warhammer C, as that would probably fit better than a Rifleman C or Rifleman IIC, even if the rest of the Star would leave it behind.
I love the Vapor Eagle, and it fits in well with the Mongrel and Nova, operating in between their movement profiles, with it's only problem being a non-Omni (though I imagine your Elementals will be riding the Eponas and Hephaestus more often). If you are looking for another mobile ride for the Elementals, the Mist Lynx is the best option from your list, with the Stormcrow being a heavier option.
If you're not caring about Elemental rides, the Horned Owl makes for a good backstop psuedo-Scout that isn't too expensive if you lose it. The Conjurer pairs well with the Vapor Eagle as well (the combo nearly tore apart a reinforced lance in a campaign we're in, if it wasn't for a couple lucky Head hits and de-legging, the unit might not have reported back).
The Piranha is a fast unit and can Scout, but I'd only bring it out to play if you face a lot of ConvInf, or you really like backstabbing with Machine Guns.