What is the risk using XP and old OS in 2020?

If you keep your antivirus up to date and avoid suspicious sites, none.

With XP however, you'll miss out on most sites by now. There is a move going on that requires a newer security standard that leaves out antiquated browsers. These are sad times for us XP holdouts. Why do they have to fix something that's not broken?

You couldn't pay me enough to use either Windows XP or Windows 7 as they are obsolete, buggy, and just downright unsafe to use to connect to the internet! If you're still using either OS you are apparently too stupid to know the difference!

you can still use avast and other AVs that are pretty good
depends what you are doing on the internet
most problems are self inflicted

All kinds of things including credit fraud. You could easily be letting someone have full access to your PC and everything connected to it 

easy, any existing exploits are still available for those systems.
with XP it is VERY easy to get hidden malware which can easily still secret data, like bank info.

windows 7 is in a soft state of still being useful but it is highly recommend to switch over to windows 10 as soon as possible (especially since it is free) 

no do not use windows xp or windows 7  get windows 10 or linux

Never use XP or outdated OS as primary. You can use it on a Virtual Machine like VMware or any. Just keep in mind that, as OS, security features, Antivirus keeps updating; Malwares, viruses, security threats does same. So using a Old OS is really big risk if you are doing plenty of Financial transactions. Thank you. 

Xp is realllly old,what's wrong with windows 7 then?

I know its gone EOL this year,i jumped to Linux Manjaro,that didn't work very well,kept locking up,so im on windows10 LTSB,which runs quite well on my 2007 Dell latitude D830

I wouldn't use XP for banking at all now. Your smartphone is safer. Maybe think about running the XP machine on Linux?

7?  Usable with care but most of the anti-virus and malware products aren't updating for it. There still is a potential free upgrade route to 10, but you'd do better, as long as you don't need helpline support, to get an OEM Windows 10 Pro. Otherwise it will need to be a full version.