Tint mixing is typically taken on among like emitters due to differences in Voltage requirements. The Nichia 219C is a low Vf emitter while emitters like the Cree XP-L HI are high Vf emitters. Mixing the two will work but one will limit the other’s performance to some degree. I put together a Sofirn C8F with one Nichia 219C, one Samsung LH351D and one XP-L HI… it works fine and the color balance is really nice.
The only thing required to run triple SST-40’s is a board that takes the XM footprint or meticulous placement of small individual MCPCB’s. But yes, it works and works well. Big draw on cells, big power output. I have 3 SST-40’s in a SupFire M6 that makes around 8,000 lumens. You can also get a quad board from LED4Power to use in a Q8. 