I will give you an example where a private key had both transactions to the uncompressed and compressed public address. It is a highly non-random private key, namely in hex format
or in Base64

The uncompressed WIF private key is:

giving the uncompressed public key:

and uncompressed public address 1NZUP3JAc9JkmbvmoTv7nVgZGtyJjirKV1 which has seen so far 78 transactions. Every coin (UTXO) you send to it will be immediately stolen by bots because the private key is well known, it's not random at all.

The compressed WIF private key is:

giving the compressed public key:

and compressed public address 1CUNEBjYrCn2y1SdiUMohaKUi4wpP326Lb which has seen so far 12 transactions. The first five UTXOs that have been sent to this address have been stolen in the same block, only the last one was snatched some weeks later because it was just dust.

You can see that a single private key can have uncompressed and compressed form and resulting public addresses and both had coins sent to either of them. Assume you had UTXOs (coins) on both uncompressed and compressed public addresses, if you import only one form, you will miss the coins of the other.


Same applies for the private key in hex form
or in Base64

which in addition to numerous transactions on uncompressed and compressed P2PKH addresses also had three UTXOs sent to the P2WPKH Native Segwit address bc1qq6hag67dl53wl99vzg42z8eyzfz2xlkvxechjp which also were taken quickly except for the last dust UTXO that lasted about two months.


Bitcoin doesn't work like Ethereum with an accounting balance system. Bitcoin uses UTXO (unspent transaction output) which is basically a "chunk" of coin. If you spend it, it's always spent completely and if you don't need to send the whole "chunk", you need to send the change as a separate smaller "chunk" back into your own wallet.