"Got a weird question I've been pondering lately. I know that 80% lowers are not subjected to the usual checks, would it also apply if you wanted it to be SBR'd? Now keep in mind, I'm talking strickly personal use with no intent on selling, just to be clear."
If your question is about the status of the 80%, then; no, it is still not a firearm until you finish it out, indistinguishable from barstock in the ATF's eyes. And since you don't need a serialized firearm to complete a Form 1 for an SBR, there is no need for it to be completed until the stamp gets back (or supposedly, ever, although you may lose your tax payment if your stamp is somehow found to not correspond to an existing firearm at some later date). Accordingly, there is no need for the lower, finished or unfinished by you, to be engraved with serial number or your information, until you go to complete the SBR after getting the tax stamp. Obviously, to complete your gun, you'd have to have the stamp as well as a properly-marked lower receiver to be in the clear.
Same reason my Hotchkiss Universal kit is sitting next to a plain steel tube in the garage, while I await the ATF getting off its fat duff (over three months at this point). Both to avoid any worry about constructive intent, and out of good 'ol fashioned laziness, I'm holding off on completing the receiver until I get the green light.
TCB