There is also encryption at the client side when using a VPN, but that should not matter for the casino.
Basically the casino only sees a connection from an IP that is not your computer directly. That's basically it.
It should not affect the performance.
Having said that, there are some known lists of VPN IPs so there is the possibility that they do something differently, but I guess they need to be certified and ensure they treat every connection as equal.
Some give VPN permits because in their customers countries licenses they don't actually fall into the jurisdictional prohibition category and site blocking is only carried out by the state government, that why VPN permits in some casinos are given specifically.
And also casinos do not want gamblers who have multiple accounts in their casinos for the purpose of exploiting bonuses or cheating because it is clear that things like this are prohibited.
And the fact that using VPN can influence the results in game is truly unbelievable, in fact I think discourse like this is just nonsense.
In fact, VPN is only used to change the IP address or divert the IP address for a specific purpose.