The difference between a website and a platform is that a platform has multiple sellers. In a platform, each seller has its own page that lists multiple products.
When it comes to selecting a theme, the first consideration would be whether it will continue updating. Since WordPress have updates from time to time, it is important to select a theme that will always update.
Creating a job website like monster.com can be very easy using Woocommerce as well. Here every ‘job’ is a product. And using the plugin product filter and easily filter jobs by functions.