Is it okay to install two desktop wallets in one PC? I mean is there a security concerns if one does that? Or there will be no problem if I do that, two different wallet software in one desktop will work well separately on one PC?
Its fine to have multiple wallets on the same computer. Just make sure that they are pointing to a different data directory (for Core and Cash).
The problem with security is hard to tell. If you are using two different wallets, Bitcoin Core and Electrum, it would not be a problem as long as you downloaded them from the official site or compiled them yourself. However, if you used an untrusted source or an alt coin wallet, the security could be an issue. There is no guarantee that there would not be malware in them.