Fifo vs Lifo vs Other Methods?

I use lifo to do taxes for btc. But i find it to be very hard to calculate when you do this.

Once you use a method for a coin, you have to stick with it entire way right?

But what about other coins you bought? Could you use lifo for btc but say fifo or any other method for other coins like say iota?

Now isn't the benefit of lifo where you sort of defer tax till later on for the coins you bought first? Thus tax savings? Or its the other way around?

Is there a weighted avg method? Example you bought say lisk but say you bought it 6 times in a year. Say you bought it at prices of $1, $1.23, $1.52, $0.56, $0.60 and say $0.66. Could you average them so when you sell it, its at an average same price?

Is there any benefit to weighted avg vs lifo or fifo?

I know if you hold longer than a year, you pay 15%. Anything less i believe its 35%?