As long as you are careful out there on the internet you should be fine. Stay away from certain kinds of websites, don't do remote sharing, be cautious about pfishing & social engeering scams.
Keep your browser(s) up to date. Firefox, for example, will be actively supported on Big Sur for some years to come. If history is any indicator, FFox will be supported on Big Sur for at least the next 4 years. For a little 'extra' protection you might consider using Firefox with two Firefox extensions - uBlock Origin & Privacy Badger.
You do not really need antivirus on your Mac. Macs are pretty self-sufficient in that regard. AntiVirus apps tend to cause more problems than they solve. That said, you might consider Malwarebytes; it's a good add-on and has a light touch on your Mac system.
VPNs are also not necessarily the answer to online privacy or protection unless it is your employer's VPN and you're only using it for work.