The term Web Servers in Bunnyshell refers to virtual machines with a load balancer in front. The way web server load balancing functions is by distributing traffic to multiple instances. When you create a Bunnyshell Web Server you create multiple cloud instances and a load balancer (the component that distributes traffic to the instances). You can either manually scale (horizontally) the web server by removing or adding more instances or you can rely on autoscaling which will scale the web server based on CPU.
On the other hand, a Virtual Machine is just a single instance. The way this can be scaled is by adding more resources to it (CPU and RAM - vertically).
So the main and the most important difference between a Web Server and a Virtual Machine is that the first consists of multiple instances and the second of a single instance.
For an app to run on a Web Server, it should expect that all instances have identical disks and identical content.
Usually Web Servers are used for big online shops, that have traffic spikes, in order to add or extract servers that serve users at the same time even in spikes and make some economy by scaling down when there isn't as much traffic.
For a Wordpress or small website a Virtual Machine is recommended.
So would it make sense to always start-off with a Web Server of only 1 node?
The answer to this is no, because self-managed databases, for instance, would not need a load balancer in front of them. Also one cannot attach additional disks to web servers but can attach disks to virtual machines.