Worke5r86 Nginx, Caddy, Apache: that makes no difference to features or user experience. Just pick the one you prefer or is available to you.
CRON is only required for a few specific extensions. They list this requirement in their discussion/README.
What you might need if your forum gets popular or needs to send a lot of emails is a queue worker. There are multiple ways to implement a queue worker, be it a service, a CRON job or HTTP hook-based (the latter has not been created for Flarum yet I believe)
Something I would add is that a hosting that doesn't offer CRON jobs will probably be quite limited if you ever need to expand your forum, as it's probably not the only feature that will be unavailable. But you can easily migrate to a different hosting when you do need those features in the future, no need to pick something more expensive too early.
