I'm going to go out on a limb here and assume you've only headed this route because someone has told you that you can make invisible money to do digital drugs or whatever so it sounds like it might behoove you to take a step back and ask why can't a thing do something instead of why can't I make more digital drugs so here goes;

• mix & match GPU doesn't work w/ windows because of how display drivers work. search DDU to find a thing that someone made because even left over mix/match display drivers don't like each other.
• different invisible cryptothings use different algos to do it a different way. now you learn more copycoins than unique algorithms
• different algos will work different ways so, sometimes, you'll find that different underlying architecture can be exploited to perform a calculation faster. go much simpler by searching CPU optimization and feature sets
• after some researching into what GPU you want to buy next, check MSRP and don't pay 150% + if you ever want to ROI. Now you cooked a card and more stuff because you neglected its TDP and/or assumed 180W 1080 wouldn't draw too much from your 250W drug store special computer but you learn that CPU and HDD have published TDP as well or you learn about a killawatt
• this wall of text you decide to only read the last line and goto whattomine.com and see how different arch can vary from one algo to the next and you go buy Titan Xp. again, you let the ghost out because it has even higher TDP and you just missed some clues on things to go search and learn more better