Macbook Pro 2016 WiFi 6 or 6e

you said yours is a 'mesh' Router. there are two methods for cross-connecting with additional access points. If you run an Ethernet cable or use power-line Ethernet connection to each access point, it does not take anything away from TOTAL over-the-air bandwidth, like this:

If you use only Wi-Fi between Access points, you lose some bandwidth to message forwarding between the access points. This usually is at the highest frequencies, so may limit your 6 GHz channel-width:

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One reader set his up with a 160 MHz channel in the 5GHz range. That setup made the 6 GHz range not work. (That setup also likely killed throughput for his 5GHz neighbors, killing their performance.) Don't do that.

If your Router is 6e capable, be sure to set a more modest channel in the 5 GHz range and then you can go crazy with a 160 MHz channel across the entire 6GHz range.

Yes, what I wrote above applies. Don't use a 160 MHz channel in the 5 GHz band, it messes things up.

Use a 20, 40, or 80 in the 5GHz band, and whatever you wish in the 6GHz band.

Also, the wider the channel, the more it is prone to being clobbered by your neighbors' data.

Yes.

No. You can still use the router.