About 6 months ago I hand built a pc specifically for Windows XP so I could launch all my old games up. Still use it as the main computer in the living room when browsing online and Firefox works great. Granted I went with a paid AVG antivirus and what not but the machine runs great and still snappy as heck. There's still a lot of support out there for older software as far as antivirus and such so I wouldn't be to afraid of using it. Honestly because it's older software you can usually buy 2 or even sometimes 3 antivirus subscriptions from different brands for the price of 1 on today's Windows 10 platform.
Edit: Also running something like NordVPN can really help in ANY platform of Windows whether it be '95 all the way to Windows 10.....