1.I am using IBKR as my main trading account.
From my statement, I notice trading 10 VUAA will cost me usd1.91 in fees/comm. There was once I bought 122 VUAA, and the fees charged were usd5.91.
How much IBKR charges you also depend on your Account settings. They have different tiers, I can't remember which tier I am on, but if you read the forum pages, you may find some good tips from other investors.
2. As far as I know, not only IBKR gives the most competitive rates, but they give the best currency exchange rates within the platform.
3. But beware that IBKR, being a US based company, may apply estate duty taxes on US shares, should anything happen to you. So, if you have a million $ in your account, the estate duty may be hefty, as the estate duty exemption is only $60,000. Just remember, don't exceed $60,000 on US situs assets. Btw, I reckon you probably know that VUAA is UCITS compliant, and therefore, not subject to US estate duty.