I read how safe and secured owning a Bitcoin Paper Wallet is, so I decided to give it a try by creating one from bitaddress.org.
Did you actually do this on an air-gapped computer or one running a LiveOS that was
offline? Or did you just goto the website and click generate?
If you did it online, you basically removed all the benefits of a properly created paper wallet... rendering if no more secure than a software wallet... and likely worse... given you're using a 3rd party website to do it.
Paper wallets can be secure, but they require a bit of work to create properly so they are actually secure.
Every private key has near infinite (not really, but close to) addresses possible. When you import a private KEY into a programme, like imtoken or bitcoin core, that programme will generate an address -- from one of the near infinite ones available.
That's wrong. Private keys do not provide near infinite addresses... HD wallets and
seeds provide near infinite
private keys.
There is a quite large number of valid addresses that can be generated from a single private key
No, there is not a large number of valid addresses for each private key. You can generate
three addresses. Legacy, Nested SegWit or Native SegWit.
so both addresses that you see should be correct and funds sent to either will arrive in your wallet, since both addresses are generated from the same private key which you imported into a wallet software.
Be aware that is not necessarily true either. While both addresses may indeed have been generated from the same private key... and imToken supports Legacy (as generated by bitaddress.org) and Nested Segwit (what it uses by default)... if a wallet does not, for some inexplicable reason, support all three... then any funds sent to an unsupported address type would
not show up in the wallet.
For instance, imToken only appears to support Legacy and Nested SegWit addresses... it does not use native SegWit addresses... So, if you sent to the native segwit address that is associated with a private key that you imported into imToken, then the funds sent to that address would not show in imToken.