I haven’t bought into smaller digital cameras yet. Luckily so far, the weight of my gear is not an issue. I see why your trying to go lighter. I think the 100-400mm lenses are typically fairly beasty. I love the range but I don’t know of any fast models, they are typically pretty slow right?
I used to use two cameras when shooting events. My last pair before going mirrorless was a Canon 5D Mark IV and a Canon 90D. I used a EF 24-105 IS on the 5d full frame sensor and a 70-200 on the APS-C crop frame sensor. This worked out well for me for the reach, and the slow EF 24-105 had IS so not so bad. I usually would take a hand held flash if the location was to dark for the slow lens. Now I only have one camera, the Canon R5. I had the notion I would use the 5D as a second body but the functionality of the two cameras was to different so I sold the 5D. Now I’ll have to rent another body until the R5 gets updated and I can buy the new model. I have very fast lenses now, and they are so much appreciated! Sorry I think I got a little off topic! 🙂