I'm the one who posted about my nephew getting screwed.
PA (with caveats) uses the rules of the other state. If VA doesn't need a notary, you don't need a notary. The reason is, since VA doesn't require a notary there is no space on the title for a notary stamp. It's not kosher to notarize something that doesn't have a spot for it, therefore PA can't really require it. If you take a VA title to a VA notary, they will likely decline to notarize it because they can't, or at least aren't supposed to.
Above all, ALWAYS consult two different DMV tag places AND check the requirements on the PennDOT website. You might need just a signed title. You might need a bill of sale. You might need a young priest and an old priest. As with any transfer in PA, you'll need your ID and an insurance card. As long as you have the state minimum liability on another vehicle, you can get stuff done. You don't need insurance on the new Nissan yet. PA insurance law (this can be more or less restricted by the company you use) gives you 30 days to add it to your policy. It is covered, provided you add it and pay the premium within 30 days of the purchase date. In theory (check with your company), you could buy it on August 1st, drive it home, do the title/registration, and hit something on the way home. As long as you call your insurance company and add/pay before August 31st, it's covered.
If VA does temp tags, do it. Once you get it back to PA, the person doing the transfer will need to see the vehicle itself to do a VIN verification and GVWR confirmation. Once that happens, they can punch some buttons, take your money, and hand you a plate and registration. You'll get the title in the mail a few weeks later. One stop shop.
Some states do a 30-day thing where a signed title is good as a temporary registration for 30 days, meaning you could drive it home. That was the case in TX, but I think it was actually 60 days. The plate stayed with the vehicle and you could just drive it without transferring for a while. Print out whatever you find on VA law concerning that in case you get pulled over in MD or WV. Out-of-state police aren't required to know VA's rules and they usually don't.
Above all, be prepared for PA to be confused. They have a big book of all the states' rules but it is sometimes wrong or not up to date. I bought a boat out of MD once. MD didn't start titling boats until the mid 80s. The boat I bought was a 1981, so no title, but the PA book said that they DO title boats and required a title. I even presented them with documentation from MD's website that said my boat didn't ever have one and they refused. Fortunately, I found a sympathetic person at the MD department of boaty things (MDDoBT) who typed up a "fake" title for me.
