Capp, cousin of 2006 Commonwealth Games gold medallist Moss Burmester, has been knocking spots of longstanding national records in recent months.
He ripped 15 seconds off the 22-year-old 1500m mark of double Olympic champion Danyon Loader, snatched the 800m mark from Dylan Dunlop Barrett and overtook Dean Kent's nine-year-old 400m individual medley record.
Capp is back under the wing of acting Swimming New Zealand coach Clive Power and enjoys his direct methods.
"I do feel like I'm ticking all the boxes," the 22-year-old said.
"Clive's done an awesome job to give me what I need to perform at my best. He's very old school, meat and potatoes kind of stuff, but I'm happy with it."
New Zealand had a disrupted journey from their training camp on the outskirts of Barcelona, spending a night stuck in an airport en route from Spain to Kazan via Moscow, courtesy of a storm in the Russian capital.
The youngest team member, Hawkes Bay's 15-year-old Bobbi Gichard, picked up a cold which cost her a day's training.
New Zealand are relishing the chance to treat the worlds as a dress rehearsal for next year's Rio Olympics.
The worlds have a village set-up for the first time, including a dining hall, with training pools dropped into the nearby football stadium, and overall mirroring what will happen in Rio.
Capp is entered in four events, and is one of five New Zealand swimmers in heats action on the opening day.
He and Matt Stanley are in the 400m freestyle; Boyle and Emma Robinson are in the women's equivalent; and Glenn Snyders has his 100m breaststroke heats.
Capp is also in the 800 and 1500m and finishes his campaign with the 400m individual medley.