QSFP-40/100-SRBD. A few questions people keep asking but rarely answer

[robertanderson]

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I am looking at QSFP-40/100-SRBD because our data center has a lot of existing duplex multimode and swapping everything to MPO would be a big project. The idea of running 40G now and stepping to 100G later on the same duplex MMF sounds perfect, but every time I search, I see the same basic questions repeated. What I do not see are the practical answers people learn only after deploying it.
Here are the things I keep hearing asked in chats and forums, but never with clear replies:

1. When you run QSFP-40/100-SRBD at 100G, does it become noticeably more sensitive to older patch panels and jumpers compared to 40G, even if the run is short?
2. Do you ever see odd DOM readings or alarms that look scary but end up being harmless? I have seen people mention power mismatch warnings but no real follow up.
3. Does your switch need any special configuration to force 40G vs 100G, or does it usually come up correctly as long as the port is set properly?
4. If you have a chassis with several of these installed, does heat or airflow become a concern, or is it basically the same as other QSFP optics?

If you are using QSFP-40/100-SRBD in production, I would love to hear what you wish you knew before buying. Did it behave like a simple drop in solution, or did it come with small gotchas that only showed up after a few weeks of real traffic?