So even if Bitcoin gets to a very skyhigh price, there will be no need to hold a whole Bitcoin to your self. We can just make transactions and save in tiny fractions.
People can make Bitcoin transactions if its amount in satoshi is equal to or larger than minimum thresholds that were set up for preventing dust attacks. They certainly don't have to buy 1 bitcoin or whole bitcoins like 2, 3, 4
BTC.
so that's it, if Bitcoin had an unlimited supply like regular Money, it would lose purchasing power and value over time
Bitcoin has its high value by other things like decentralization, censorship resistance, and strong network security as well as non custodial instinct for users.
Altcoins can have lower total supply than Bitcoin and they can have burn programs too but all those things don't make altcoins are more valuable than Bitcoin. Bitcoin has no buy back and burn programs so far in its blockchain history.