Confusion over Swap Fees and Withholding Tax

I’m trying to decide between Vanguard S&P 500 (VUAG - Accumulating non-hedged) and Invesco S&P 500 (G500 - Accumulating Hedged).

I’m investing via my ISA. Is there a Withholding Tax for U.S S&P500 ETFs domiciled in Ireland, for UK residents? I’ve read conflicting information on this, unless I’m just misunderstand it.

Here for example it says:

UK investors are exempt from withholding tax on the income they receive from ETFs domiciled in Ireland and Luxembourg.

But then says:

ETFs and other fund types also pay withholding tax on the dividends and interest they receive from their underlying assets purchased in other countries. For example, S&P 500 ETFs pay withholding tax on their US shares even if the fund is domiciled in Ireland or Luxembourg.

This website says:

US equity ETFs domiciled in Ireland have a 15% withholding tax rate on dividends versus 30% for ETFs in Luxembourg and other jurisdictions.

Also, are accumulating funds classed as dividend payments for purposes of tax? Even though it’s automatically re-invested into the fund?

2nd question is on the swap fees. The Invesco fund has a swap fee of 0.3%. Is this fee 0.3% of your total investment per annum? Like for example, my investment is standing at £1000, and I’ll pay 0.3 of that?