Crucial Topic.
Custodial wallet is a type of wallet that requires a third party to takes hold of private keys on behalf of every user.
Which makes asset more secure, because only the third party and the user knows the private key.
In a case where there is missing asset, the private key must have been shared to someone outside the third party and user.
As for Hardware wallet, just misplacing it could put the user at risk, because no third party to help checkmate the security.
The bolded part of your post caught my attention. I'm not sure by what you mean by "makes it more secure".
Are you implying that using a custodial wallet makes your coin more secure or what? The fact that it's called a "private key" and not a "shared/public key" should already give you the idea that its not meant to be shared with others only the owner of the wallet should know the private key of his or her wallet.
To the Op, if you're unable to afford a hardware wallet then you can also use some reputable non-custodial wallet like Electrum, you can use it has a cold wallet and that will provide the same security as a hardware wallet.
The way you use your wallet determines how much secure your coin will be. but if you decide to be careless with your wallet even if you use the most secure hardware wallet your coin might still be stolen.