Yes, I will be accessing financial data through various bank and brokerage web sites and then file taxes online, and I believe they all show the "padlock" symbol.
In this case, assuming that all of the institutions have properly implemented their encryption protocols, all received and transmitted data should be protected.
Would a VPN or personal hotspot provide additional security?
For your particular purposes, using a VPN, hotspot, etc... will only really provide security in the sense that an eavesdropper won't be able to see the type of internet traffic passing through your computer. In other words, she won't easily be able to tell whether or not you're browsing the web casually or making financial transactions. If this type of privacy is important to you, then you might like to try those options. (But keep in mind that the provider will have access to your usage habits.)