Any issue with Sims is likely to be more related to when/whether Sims is recompiled for the new architecture.
I'd suggest waiting a couple weeks to see what folks report as systems begin to get into users hands. First orders should be delivered early next week. Until then we're largely working from guesses and supposition and hearsay.
Same for actual info on the differences between the MBA and MBP in running applications.
Anyway -
Dunno what canva is, other stuff should be fine on either option.
To use a 2nd screen, it should be as simple as plugging in a USBC to HDMI (or Displayport or whatever your monitor needs) cable between computer and monitor, with power plug in the other port. If you want to use other stuff, a USBC or Thunderbolt3 dock should work well. Wide variety of options. I'm currently using an inexpensive one from Amazon with my 2020 MBA -- with the single cable connection I have an external drive for timemachine, 1080p HDMI monitor, and power. No, I don't know if it'll handle 4K displays or fast HDDs, but it works fine for what I have.
LENTION USB-C Digital AV Multiport Adapter with 4K HDMI, 4-Port USB 3.0 and Power Delivery (3.3FT)
www.amazon.com