TDP (Powerlimit slider in MSI AB) is just one part of the OC equation that people often don't even fully understand. It's the maximum allowed percentage of the "total" power that the card is allowed to burn. The thing is, the "full" TDP differs from card to card, it's a value in the card's BIOS, yet people in the forums often share their set Powerlimits like they're universal between different cards. They're obviously not. Your MSI 1070 cards might be higher-end Gaming (X/Z) cards and their factory TDP might be well above the reference 150W. Could be 180W, or even more. So when you set your powerlimit to 70% with these cards, you're telling them to burn no more than 180*0.7 = 126W. Not that much of a limit for a 1070. But your EVGA 1070 Ti cards might have their TDP set to 180W in BIOS, yet it's a more power-hungry chip, so when you set PL 80 for them you're limiting them to 144W, which might just not be enough for +200/+600 mode that you initially set.

I'm not saying it's the powerlimit setting that is the reason for your troubles in this case (although it could be), just trying to explain that controlling voltage and clocks on Pascal cards by simply moving one powerlimit slider is not very precise and reliable, and any meaningful tuning with this slider at least requires the user to know the actual (100%) TDP for the particular card in Watts.