I was under the impression that the V-brake quick release nipple would be of such a size that you could get a good brake feel and still disconnect the brakes without any further adjustment.

On my family's bikes this does not seem to be the case!

All of them have very soft brakes if you adjust them so the nipple & noodle can actually be pulled out. So I compensate by making several turns of adjustment on the brake lever cable adjuster - my concern with this is that fewer threads engaged in the brake lever means more risk of damage under load.

Is this a fundamental design flaw with V-brakes or just a reflection of the off-brand brakes on our bikes?

And would I be better served by just ignoring the quick release function and focusing on getting the best brake feel without needing to adjust the cable?

the quick release should be able to be used without adjusting the brake every time....
maybe post some pics and show us what it is you are doing.

Make certain that your brake cable housing ends are properly prepared (ground of filed flat) and fitted with the correct metal ferrules where needed. Unless the adjuster is almosr coming out of the brake I think you needn't worry about them failing. There is nothing wrong with backing off the adjustment a few turns when you need to open the brakes and then readjusting it when you put things back together.

Do the brakes stop satisfactorily? Having a hard lever feel does not equate to having good braking, and adjusting them tighter to the rim doesn't change the feel significantly but only makes them grab sooner in the lever travel. You might also consider changing to a harder brake pad compound. You might also be feeling flex in the brake arms themselves or of the fork.

Some levers pull more cable then others, either from actual leverage design or the lever's ability to pivot a larger amount before contacting the grip (and a thick grip limits this). Also some V brakes have a spring loaded cable stop on the guide noodle. So sometimes the amount of cable pull to create solid pad contact is less then the amount to have the noodle's nipple clear the clip.

A simple solution is to redo the cable clamp and cable adjusted position so all is good with the lever's adjuster somewhat out. Then a quick turning in of the adjuster should allow enough nipple/clip clearance to release. Andy.