Since we planned on traveling 12 months originally, we had a lot of contingency plans.
First of all, from a $$$ standpoint we diversified our access to money. Between DW and I we did the following;
Each brought $1k in USD and $1k in Euro (Cash)
Each Opened Schwab Checking and SoFi Money Accounts (both don't charge foreign transaction fees AND reimburse foreign ATM Fees), we funded these accounts with $5k each (for a total of $20k spread across 4 accounts)
Each made sure to have two different Credit Cards that didn't charge foreign transaction fees (Hilton Amex and Cap One Quicksilver)
Then on top of that we had our regular debit card and and credit card from our local bank in case of emergency (they charge foreign transaction fees).
We were able to use the Schwab and SoFi debit cards in any ATM in PT and received up to $500/day each from each account if we needed it, in Euro, with no fees at basically the Forex exchange rate, which was better than exchanging at a money house or physical bank!
Using Credit Cards was also no problem, and the Capital One Visa was accepted everywhere, while the Amex was only accepted in specific stores.
We also paid for accommodation online through AirBnB, so the remainder of our spending ended up being <$1k/month anyway.
Some banks like Capital One let you verify your login to the website through the mobile banking app, but we never had to do that.
For cell phones, DW had ported her long time phone # to google voice and used WiFi exclusively while in PT. In Poland she got a local sim and phone plan which cost like $8/month for 10gb. I went an entire month in Portugal on WiFi only (it was glorious not having a phone/data in my pocket as an experiment for a month!), but then I caved and got a local 10gb prepaid sim for 20 euro, keeping my AT&T sim in case I needed to dual factor in an emergency. I think AT&T charges $10-15 per day if you use your phone abroad. So I took the sim out and kept it stashed in my backpack to swap incase absolutely needed to (never needed to).
As far as stuff like Vanguard and Quickbooks, I have no idea unfortunately.