CH ...how important in a vinyl pool??

Do you have any chemical values to uphold to maintain warranty on liner or heater? If not then you are fine. There's no plaster to etch.

I like to maintain mine around 75ppm minimum.

Sometimes you can get foaming, if you have very little ch.....keeping it up a little prevents it.

Simple answer is that for most vinyl pools, low CH isn't an issue as long as it is above 50-75ppm. Super low CH can lead to foaming. Some of the really cheap vinyl liners have calcium as a filler in the vinyl material. Keep some CH in there and you should be fine. Be cautions since calcium scaling can still occur on a vinyl pool if the water is oversaturated with CH.
Although some equipment mfg's require a specific CH to maintain their warranty, the reality is that the equipment (aka heater) does not need any CH in the water. The wet components don't contain any calcium and therefore won't leach out any CH to the water and cause component failure. My gas fired hot water heater (and all components on the hot water side of the house plumbing) in the house sees zero CH water due to an installed water softener and it operates just fine. In fact I'd be willing to bet a hefty amount that the plumbing system prefers no CH in the water.