I regularly use Transferwise for sums up to $15k, money arrives in my UK bank same day if I wire the money to TransferWise in the morning. I’ve also done $15k transfers on consecutive days without a problem, but I agree that with a sum of, say $50k, it would be worth asking banks for the “dealing desk” rate and comparing.
The year we bought our house here I not only triggered FBAR bit also FATCA when I filed our IRS return. That was because of the stupid accounting the IRS uses. I transferred the house money to our checking account then put it in our savings account for a while until the house purchase was completed. This meant it was double counted for FATCA purposes so needed reporting (no extra tax just more hassle filling out forms) I should have transferred the money direct to our savings account and then direct from there to the lawyer for house purchase.