I know a blockchain wallet is a safe way to store, manage, and spend your cryptocurrency. I know all about the types of wallets ranging from Cold storage to hardware.
If you refer to blockchain.com wallet, it's not that safe compared with hardware wallet or wallet software installed on your device.
Recently I decided to use a VPN when carrying out a transaction. I know I am not that techy but I have got to ask, is there / will there be a security issue when handling such transactions?
Assuming you're talking about blockchain.com wallet or another wallet which accessed from browser, there's security risk where malicious VPN manipulate DNS record to make you visit fake website.