You can buy $500USD per day no questions asked. If you have ATM receipts or receipts buying RMB with USD, you can change more. I bought $2,400 one day at the BOC at West end of Nan Ping Jie a couple of months ago.

You must declared $10,000 or more on entry to the US. Don't think there is a limit but I am sure they will ask

questions.

Think to wire, or Western Union, USD requires the USD in hand when you do it.

I live off my US money, income, so I have lots of ATM receipts.

Made it to the Laos Consulate, about a 40 kuai taxi ride from Bei Chen Da Dao, Walked from the security gate to the consulate and got quick service. But left without a visa.
If you are an American, you get your visa at your entry point. Sorry about that.
Getting a taxi back home is nearly impossible. It took more than one hour to get a taxi. Was unfamiliar with the bus numbers and the bus signs were so dirty even the Chinese couldn't read them.
See you in Vientiane!

I am planning a trip to Vientiane, visa run. You can buy $500USD per day at the Bank of China downtown on Dongfeng Xi Lu. No questions asked and it is simple. Bring your passport, RMB, and fill out a form, it has English labels for the stuff they want to know. Normal questions.

If you changed USD to RMB, like using your US ATM card in Kunming, and have the ATM receipts, you can buy USD up to the value of receipts. I got $2,400 in one trip a few months back.

Check the USD you get carefully. Give back any worn, wrinkled, old or defaced bills. Hard to unload them for kip, baht, dong or yuan.

Is a visa run to Laos doable? I'm gonna need to do one and also need to go to Vientiane as well

Best I can tell these changes apply only to ethnic Chinese. Only one item did not mention "Chinese" but it referred to living with "immediate family" which may include a Chinese spouse.