Earlier quoted context omitted.
I'm not sure whether their fees are really that low. For transfers between your own accounts, for anything over very small amounts, I found that their 0.35% variable fee is pretty large compared to adding the funds to a brokerage account and then doing the conversion there (ie. IB charges 0.002% on currency trades, with a min of $2), and transferring back out into the desired currency.
Could you explain how this works, or point me in the right direction on what to read? I'm interested in not using Transferwise as much if this is better.
You'd open up a trading account, deposit funds from one country to it (generally free in EU/UK, can be done with a simple bank transfer, though can take 1-3 business days). Rather than the common use case of a brokerage account to buy stocks/invest, you place an order into their IdealPro order book they run to buy the currency you want (might have to jump through 2 trades, they don't run every single pair). Generally this is tailored at larger investors, so anything under $25k is subject to some additional fees due to being a small size (https://ibkr.info/node/1459), but still significantly less than the 0.35% TransferWise charges. The costs for you are commission (<0.2bps), potentially small size fee (1-2 bps), and crossing the bid/ask spread, which is ~0 for currencies). When that order has been filled you now have the desired currency in your account and you can transfer it back out (potentially to a different country or different account).