You can check it by opening chrome://webrtc-internals in a tab before you join the conference. After joining, you’ll see 2 peer connections there: 1 for the p2p connection and one for the bridge connection. Find the active one by checking there is media flowing (bytes move) in the send SSRCs.
If you expand the video SSRC you’ll see something like image below:
The highlighted properties indicate if the resolution was cropped due to bandwidth or CPU limitations.