The impact of a VPN on internet speed and overall performance can vary based on several factors. Firstly, the encryption process, a fundamental part of a VPN, requires additional processing power, which can slow down the speed. Secondly, the distance between the user and the VPN server can affect latency; the further the data has to travel, the longer it takes. Thirdly, the load on the VPN server – the number of users connected to the server at one time – can also influence performance. High-quality VPN providers invest in powerful servers and optimise their networks to minimise these impacts, but some degree of speed reduction is generally inevitable due to the encryption and routing processes involved.

While VPNs greatly enhance privacy and security, they don't provide complete anonymity. A VPN can mask the user's IP address and encrypt the data transmission, making it difficult for third parties to track online activities or determine the user's true location. However, the VPN provider itself can see the user's original IP address and often the destinations of the user's internet traffic, depending on the encryption and VPN protocol used. Some VPN providers maintain logs of user activity. Therefore, absolute anonymity isn't guaranteed, especially if the VPN provider is compelled by law to disclose user information. Users concerned about anonymity need to choose a VPN provider carefully, considering their logging policy and jurisdiction.

Firewalls play a critical role in VPN deployment, acting as a gatekeeper to regulate VPN traffic alongside regular internet traffic. In a typical VPN setup, the firewall is configured to permit traffic to and from the VPN server while still blocking unauthorised connections. This configuration helps in safeguarding the network against potential intrusions or cyber-attacks that might try to exploit the VPN connection. Furthermore, in more advanced setups, firewalls can inspect VPN traffic (once decrypted) to ensure that it conforms to the organisation's security policies, thus providing an additional layer of security. Effective use of firewalls in VPN deployment is crucial for maintaining the balance between accessibility and security.

A site-to-site VPN and a remote-access VPN serve different purposes. A site-to-site VPN is used to connect entire networks to each other, typically linking branch offices to a company's main network. The VPN allows for different networks, possibly in different geographical locations, to securely share resources and data as if they were in the same physical location. Conversely, a remote-access VPN is designed to connect individual users to a network. This is commonly used for remote workers who need to securely access their company’s internal resources and applications. While the site-to-site VPN is like a secure bridge between two separate, fixed locations (networks), the remote-access VPN serves as a secure path between a mobile user and a network.

A VPN ensures data confidentiality and integrity primarily through the use of encryption. When a VPN connection is established, all data transmitted from the user's device is encrypted before it travels over the Internet. This encryption is like converting the data into a secret code, which can only be deciphered by the correct decryption key, typically held only by the sender and the receiver. Consequently, even if the data is intercepted during transmission, it remains unreadable and secure. Moreover, integrity is maintained as any tampering with the encrypted data can be easily detected due to the nature of the encryption algorithms. Advanced cryptographic techniques ensure that even minor alterations in the encrypted data will produce significantly different decrypted content, alerting the receiver to any potential integrity breaches.