I feel like 70/70 + 70/x could work, but my knowledge on pet fusing is very limited, so I’ll have to say that I don’t exactly know. If you have already done what you are planning to do (maxed 1+2 for first, maxed 1 for second), select the pets you want to combine and see what message appears. If it’s a “Good Fusion,” then your outcome Legendary will not reach its 90/90/90 potential. If it says “Maxed Fusion,” it will. If what you have said is all just a plan and you haven’t done it yet, you should probably ask a more experienced person. Let me know if you ever find that answer, I’m actually curious myself!