My Genesis Day One has mini v brakes. Would cantis like Avid Shorty’s be more powerful? And would it be necessary to have some sort of thing on the headset to hold the cable in position?

I just recently swapped out my tektro cantis for mini v’s, all the while i was using the cantis i was tottaly happy with them, now that i’ve got mini v’s i don’t think i could ever go back. Stick with with them imo.

Agreed. Mini v are more powerful than canti brakes. However, they feel more spongy (due to mechanical advantage) and need to be set closer to the rim.

Ok. Must just be rider weight that’s the issue 🙁

If its anything like my Day One the mini V’s eventually seize up as the pivots corrode. I bought some XLC ones to replace them which worked lots better and have brass bushings, very powerful. More so than my road bike brakes. They were like these though i got them from parker international.
https://www.greyville.com/products/7083

The front one has done just that. I’ve ordered two of those you suggest. £8 each. Seems very cheap, presume they’re just not gucci, rather than shi te?

Worth considering some decent pads, rather than the stock ones. That’ll help too.

Oh, and yes, mini vees are better and no brake judder….

Assuming it is singlespeed, you could use some proper V-brakes, with suitable levers. eg Tektro RL520 have the correct pull for V-brakes.