3cx has really done some development in recent years on their windows platform based PBX. Most notably in the area of its hosted web meeting platform and its integrated apps.
The web meeting uses google web RTC, this means there is no client software to install, you can host a web meeting using 3cx phone app, and the recipients only need to have a PC headset, or mic and speakers / web cam and it is all done with google chrome.
3cx allow for a 10 participant web meeting in the standard license, and a 25 participant license in the pro version license.
In addition 3cx also now have an enterprise license that can enable you to have a fully redundant server for ultra mission critical environments.
This option doubles the cost of the purchase license, but I think this compared to the cost of trying to do this with other black box PBX systems is still very reasonable.
In fact you dont even get this option with most black box key phone systems or even PBX systems
3cx enables you to forward schedule web meetings using the end user app, which will automatically create calendar events.
You can also do a start meeting now option, and copy the link then email to intended participants, for on the fly meetings.