We ate quick service every day but always checked same-day reservations after scanning into the parks. Lunch reservations were always available, at least initially at 9 AM. We loved Ristorante di Canneletto in TDS and had no problem getting any lunch slot we wanted, same-day. We also saw a line for walk-ups at that restaurant when we checked in for our reservation. That was our only theme park table-service meal.
When we did counter service, we mobile ordered. Our favorites were Grandma Sarah's Kitchen in TDL and Snuggly Duckling at Fantasy Springs (maybe we were just really hungry, but we loved the cheeseburgers topped with some sort of bologna and slaw. they were more interesting than your typical theme park burger). We wanted to see the inside of the Frozen restaurant, but we weren't in love with the menu options, so we mobile-ordered iced coffee there one morning and enjoyed the ambiance. The only way to get into the Fantasy Springs quick service places is with a mobile order.