Use Electrum wallet and create a watching-only wallet on your desktop...
Then get a computer that doesn't have any internet connection and create a cold storage wallet with Electrum. Since it has no internet access it can keep the private keys (your bitcoins) there.
https://electrum.readthedocs.io/en/latest/coldstorage.htmlYou have actually reversed the order in which a cold wallet should be made. First you need to create a standard wallet on airgapped device, and then use master public key to create watch-only wallet on online device.
what is the best secure wallet can i setup on desktop computer ?
If you're going to hold that much amount of bitcoin, mate just spend the $70 and go buy a cheap Ledger Nano S[1]. It's a small price to pay for your security. This is definitely something you don't want to cheap out on.
Even if one uses a hardware wallet, it does not mean that they will be safe from
hacking, and by that I mean those users who save their backup in a completely inappropriate way (cloud, email, on PC desktop ...), and those who think that seed words are something that is normal to type around on any site that is asking for that.
Tell someone "buy a hardware wallet and be safe", actually is only a partial advice, you also need to give him advice on how to use it safely.