@cncmodeller Mixing is totally fine for the most part. Its mostly recommended to only mix the same types of resins together and some recommend even the same manufacturer. I saw a post on reddit about the Fast/Tenacious mix and tried it out. I ran a few calibration prints after mixing and altered the print settings accordingly to get the calibration print dialed in.
The Tenacious only comes in Clear Yellow and Obsidian Black. I ordered the Fast in Smoky Black and the Tenacious in Obsidian so all the mixed resin parts are just black. But other colors will obviously produce other final colors and may need print settings adjusted as needed