In the Georgetown area, most restaurants and stores (including convenience stores) will accept credit cards with no issues. The street food vendors will likely accept Grab or Touch-and-Go, as well as cash. I've found very few places that were absolutely cash-only, the notable exceptions being the toll bridges and paid-parking structures at the shopping malls which seem to be T-n-G only. Once you leave Georgetown, which heavily caters to tourists and expats, it might be a slightly different story.

It might also be reasonable to instead just exchange a small amount of cash (Maybe 20-50 usd) just to have some pocket money. You'll get a less favorable exchange rate, but you won't need to pay any ATM fees.

You definitely want to establish a grab account and link your credit card. It is the primary app for ride-share and food delivery services. You don't need to fund the grab wallet ahead of your transactions if you have a linked credit card.