Should I go vwrd because I only have to fx once from sgd to usd instead of sgd to usd to gbp?
Interactive Brokers offers both GBP.SGD and USD.SGD, at least via IdealPro. So that's not a reason to prefer one or the other.
Or is gbp '' cheap '' now so I should go vwrl?
That's not a reason either. VWRL and VWRD hold exactly the same assets. Those assets are merely
expressed at any/every moment in time using both British pounds and U.S. dollars. If the exchange rate between those two currencies changes, but nothing else changes, then the nominal price figures for VWRL and VWRD will perfectly adjust in exact mirror image to the exchange rate change. If that didn't happen, automated trading would immediately step in and trade against that imbalance to correct it, in the blink of an eye or faster.
Also, I noticed that the dividends are not reinvested... Does that really matter?
Yes, it matters a little in terms of convenience and efficiency. Ideally, for your purposes (age 26, long-term investing) dividends would be reinvested. But they aren't, and there isn't any other single, low cost fund that covers all the world's stocks like VWRL/VWRD does. So all you have to do is make your monthly purchases
inclusive of any dividends that are paid out.
I can just add the dividends into my dca and invest them all again right?
Exactly.
So why should you favor VWRL over VWRD or vice versa? There are a few possible reasons. One reason is that IB's commissions are structured slightly differently depending on whether you're using U.S. dollars or British pounds to buy something on the London Stock Exchange. Check their commission schedule to see if that difference matters, and how much.
Another possible reason is that either VWRL or VWRD has more "Assets Under Management" and thus, on average, more liquidity/tighter bid-ask spreads. But that's unlikely to be a major factor. They both probably have ample trading volume for your purposes. They're both rather large funds.
Yet another possible reason is that, oddly enough, VWRL and VWRD both pay out dividends in U.S. dollars. So that would argue in favor of VWRD, since it's a little simpler to reinvest dividends that are already in the purchase currency.