It's true, Microsoft office can be very limiting when working with types and fonts, which is why I know a lot of designers won't recommend it.

Some small businesses choose to use online platforms such as Canva for quick and easy designs because it contains a lot of templates and a lot of modern typefaces too. Designers tend to carve their own path and they prefer tools like Photoshop, illustrator, Adobe XD or Figma.

It's an unwritten rule to avoid types like comic sans like a plague. It's been overused and cliche for a long time.

To convey seriousness, I'll suggest sticking to either serif typefaces of purely sans-serif typefaces. Anything else with a bit of extra curve can be distractive and may lose the gravity of the message. I'll give a few recommendations below:

Sans category: Montserrat, Helvetica, Lato, Avenir, Wavehouse, TT norms, Futura. A lot of modern websites tend to use sans serif for website copies and flyer designs. Maybe that's why on Canva.com, they simply grouped them as 'corporate fonts'.

Serif category: serif fonts are also great for corporate flyer designs and websites too. Especially when it's wants to connote trust, stableness and reliability. I like using Georgia, Garamond, Andalus, Merriweather, etc

As someone who's fairly new to this, I've learnt that it's easier for me to combine sans types with sans types and serif types with serif types. Trying to mix it is pretty hard to get right.

I found a good resource online that can help with picking the right types. http://typ.io/lists/serif_fonts_for_headers