Why do top fencers' blades bend so much more than mine, and should I get a stiff or a soft blade?
Mostly it is speed and the camera, not soft blades. Elite fencers move the blade faster and change direction harder, and a long steel blade bends under its own momentum every time the hand stops or reverses. Broadcast slow motion freezes bends your eye never catches at full speed. Phone video can exaggerate it further, because most phone cameras record each frame line by line, which makes fast-moving thin objects look curved. Film your own bouts, slow the clip down, and you will see your blade bending far more than you thought.
Every legal blade is flexible by design, and the rules set the range. The test clamps the blade 70 cm from the tip and hangs a 200 g weight near the end: a foil blade must bend between 5.5 and 9.5 cm, an épée blade between 4.5 and 7 cm, and a sabre blade between 4 and 7 cm. Inside those limits, manufacturers sell the same blade in different grades, usually labeled soft, medium and stiff. Even the stiffest legal blade bends a long way when it lands.
A stiffer blade follows your hand more closely. The tip goes where you point it, settles quickly after a beat or a parry, and is less likely to slap flat on a hit. A softer blade is easier to flick and to bend around a parry, but the tip lags behind your hand and wobbles, and soft blades pick up kinks sooner. For most fencers past the first months, medium or stiff is the sensible choice, and fencers who rely on precise point work generally lean stiff. Borrow club mates' weapons for a bout each before you buy.
The dramatic bend you admire comes from technique, not from buying a different blade. Point control lives in the fingers and wrist with the arm extending smoothly from the shoulder, so practice it directly: ten minutes of hitting a small target on a wall pad or a hanging tennis ball, from a lunge and from an advance lunge, does more than any new blade. Forearm and shoulder strength helps too, and flicks are a timing skill your coach can drill once your basic hits land reliably.