I mostly use Zoom and Webex, but both have an option (usually accessed via a little arrow next to the mute button) to open settings. Both give you the option to choose which mic/speakers you want to use and both allow you to do a test record for a few seconds and then have it played back to you.

I know in Webex you get this option before you are connected to the actual meeting, but Zoom may have it somewhere else I haven't bothered to look for. I make a habit of testing my mic every time I connect to a meeting, just in case I mucked something up or there's some other issue I wouldn't have known about. It's a minute of checking to save several minutes of embarrassment and delay later on.

Using the Zoom "record in the cloud" feature should roughly correspond to how people hear you BUT it does not let you know if eg your setup echoes someone else's voice. Bother someone, find a friend, ask your manager, geek out about audio, something.

There's a way to launch a "test meeting" where you can hear yourself as others would: https://zoom.us/test

Just listen to your own audio? In windows there is a checkbox for this, and most call apps have a settings page where you can listen to your own mic.

Not really. Zoom applies lots of noise canceling and other filters, so your raw audio doesn't correspond to what you actually sound like to other people (unless you use "original audio").