Do VPNs work?

On a home internet connection with password secured wifi or ethernet, privacy isn't a huge worry. Microsoft and Google will still be mining your data whether you have a VPN or not. If on public wifi somewhere, a VPN is a must.

With VPNs things get murky. Some are decent, some are not, and some you just can't tell. It will really depend on the VPN you choose. Some of the not decent ones store your data.

Will it affect speed? YES. The VPN provider I occasionally use (Nord) has not had a single server yet that can even take advantage of my gigabit connection and my PC connected by ethernet. Speeds vary significantly between servers. I've come across a few that are pretty fast (100-200mbps) but many are much slower in the 30-40mbps range. I have tried a few other VPN providers but none of them had faster offerings so far.