Since we all know that the price of the BTC is going up and down and we can't clearly know what's going to happen in the next month, few months, a year... Would it be "better" maybe to keep 51% of your btc in fiat? or some other proportion IF the bitcoin price somehow crashes like it did when it came from 1k to about 200$ so if that does happen you can still cover the "loss" of your btc in fiat and if the price goes up you can still convert that % of the gained btc to fiat, so you always have a backup in some dark case. Thoughts?
you can't just set fixed numbers like this.
if you want to invest in bitcoin for long term then you should but whatever amount you can afford to risk and don't think about small daily changes.
but if you want to trade bitcoin daily then you should do it completely not half ass. which means buy all and sell all your investment in appropriate times to take the biggest profit.