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Is there a place online to monitor this?

dappradar works well for seeing volume on dapps of course https://dappradar.com/rankings/protocol/wax

you can also get some stats on Bloks https://wax.bloks.io/live

That live WAX transactions page is pretty cool!

Can you give any advice on coming up with a baseline for 'average activity' or something like that?

Just so I can easily see if the network is jammed or quiet?

WAX is so active it's hard to get a baseline, i just look at the total CPU usage, etc... to make a slightly educated guess