i use the powerlink on my 2080 ti but just bought a evga rtx 3070 ti ftw ultra off ebay so should i use the powerlink or not with 3070 ti?

I don't see why not..The PowerLink is rated for up to 300 watts, same as the 8-pin PCIe supplemental power connectors are @ 150 watts each..There's also the mobo PCIe slot itself that's rated for up to 75 watts.

The card could get up to 75 watts from the PCIe slot and 150 watts from each 8-pin PCIe supplemental power connector.

So you have a 290 watt card and it could get up to 75 watts from the PCIe slot which leaves 215 watts needed from the supplemental power connectors which is well below the rated 300 watts of a PowerLink.

PCI-SIG specs dictate that a PCIe slot be rated for 75 watts, a 6-pin PCIe supplemental power connector for 75 watts, and an 8-pin PCIe supplemental power connector for 150 watts..But it's the card's VBIOS that actually controls how much power the card draws from the slot and PCIe supplemental power connectors.

I would use a PowerLink on your card and wouldn't think twice about it.

The problem may be getting it to fit.  If you do a forum search (Yeah, it's working again) some members have modded them to fit on various 30 series cards. I do not know if they fit on the 3070 Ti FTW.
 
Hope it works for you.

oh yeah the 3070 is bigger. ill see when i get it in my hand. 

 

freakdaddy64
oh yeah the 3070 is bigger. ill see when i get it in my hand. 

But if it fits, or you can mod it to fit, then there's no reason electrically that I would not use it.
 

It did not fit my 3060ti FTW Ultra.

good to know my 3070 ti ftw3 ultra arrives tomorrow