What's the difference between VWRA and VWRD? Should I be concerned about VWRA's lack of performance history? Is VWRA accumulating, denominated in USD and Irish domiciled?

It’s the exact same fund, only difference is how the dividends are handled D(distributed) or A(accumulating).

The performance is going to be the same between both funds ie if you buy VWRD and manually reinvest the dividends you get the equivalent of VWRA.

https://americas.vanguard.com/institutional/mvc...

https://americas.vanguard.com/institutional/mvc...

They are different share classes of the ETF.

FTSE All-World UCITS ETF - (USD) Distributing (VWRD)

FTSE All-World UCITS ETF - (USD) Accumulating (VWRA)

As for which class to go for, depends on your strategy and brokerage used.