if my battery shows 356 cycle count how much of a life it has

Yes, unfortunately BATTERY CYCLES dont mean of anything, contrary to very popular myth.

I can easily, if so inclined, destroy a battery with low (~ 300, 250, 400) cycle counts.

While cycle count is commonly seen to be the “miles” on your Lithium Ion pack cell in your Macbook, which they are, this distinction is not a fine line at all, and it is a big misconception to “count charge cycles”

*A person who has, for example, 300 charge cycles on their battery and is recharging at say 50-60% remaining of a 100% charge has better battery usage and care than another person who has 300 charge cycles at say 15% remaining on a 100% charge.

DoD (depth of discharge) is far more important on the wear and tear on your Macbook battery than any mere charge cycle count. *There is no set “mile” or wear from a charge cycle in general OR in specific. As such, contrary to popular conception, counting cycles is not conclusive whatsoever, rather the amount of deep DoD on an averaged scale of its use and charging conditions.

(as a very rough analogy would be 20,000 hard miles put on a car vs. 80,000 good miles being something similar)

Gaming: In cases of heavy and frequent use in gaming it is recommended, if possible, to keep your Mac plugged in since these frequent fast and deep discharges of the battery are not ideal for battery longevity.

Some people have 1800 cycles before "Service Battery", some have 200.

Watch "AppleMenu > About This Mac > More Info > Power" and watch it over time.