Nice plan. I’d also check your bike setup: set the saddle so your knee has a slight bend at the bottom of the pedal stroke and aim to spin 80–90 rpm; a low seat or slow grind is rough on knees. On walk days stick to flat, even paths and skip long downhills early; if you feel any knee grumble the next day, hold the same duration another week before adding time. During the warm-up, 1–2 minutes of easy marching and leg swings helps joints feel ready.
Solid pick though if stabilization is your top priority the Akaso V50 Pro/Elite or Brave 7 LE have noticeably stronger gyro EIS than the EK7000 and keep it working at 4K30. They also do a bit better on wind noise and overall mic quality. Whichever you choose, a chest mount for biking, a low deck mount for the kayak and and a little foam wind muff will smooth things out more than bitrate tweaks.
