On public WiFi I just vpn into my home network. The issue with public WiFi is that it can be sniffed by anyone in range since there is generally no encryption.
Although pretty much everything we do is over tls these days, and DoH helps protect against even dns sniffing. There’s still at least some risk to working in the clear over a public WiFi network. At least in information gathering, what bank you use, etc.
But, there’s no real benefit in using a paid vpn over one you own unless you’re downloading illegal content, want to watch another Netflix region, or are in a country with heavy Internet monitoring/filtering.
Well, I would say bittorrent with a good vpn or, usenet with a good indexer and depending on how much you download, block account vs monthly.
Personally I top up all my block accounts whenever I see a sale. With priority set from cheapest per gig to most expensive (so the pricey ones are only used as fillers).
But that does involve paying some money, but then doesn’t really require a vpn. In the long term I don’t think I’m paying that much though.