Macbook charge while using

... is it really safe to charge it while using...

Yes: About Mac notebook batteries - Apple Support

... does it really preserve battery cycle count?

If you do not use the battery then it will not be permitted to "cycle", and if you want to derive the most longevity from the type of batteries Apple uses in their products, then use them regularly.

Determine battery cycle count for Mac notebooks - Apple Support

Elizalde_06 wrote:

hello so about the battery cycle count and longevity, is it better to charge it while using to not use the battery? Im sorry i did not get that part

Charge it when it's convenient to do so. Usually that's when you're seated at a desk or in an office, etc. Just use the battery once in a while. If you were to leave it plugged in all the time, as in all day every day week after week, it won't last as long.

I keep mine plugged in whenever convenient to do so. Neither your computer nor battery will overcharge.