As a complete overview:
It depends, mainly on what you want out of your LoRa network.
Reliability, speed, range etc. are all situational requirements.
Lower BW means more range, but less speed. So 62.5 BW will reach further than 125, however it'll have slower speeds. Also lower BW means more channels/bands, as they use less frequency range.
MC uses 62.5 which allow 4 bands on Europe legal frequency range(idk about other places).
MC uses band 4, the last one, centered on 869.618(roughly rounded, should be actually 869.61875 which is closer to 619 actually).
To avoid MC interference, one should use one of the other 3 bands, or use 125 by centering on the first band of 2(for BW 125 you have 2 bands in total).
I.e., i'm using 869.556250 which is the center for band 3, just below MeshCore band. In theory they should not overlap if both systems are centered correctly.
Best settings are volatile, so to wrap it up to avoid MC you need to not transmit in this frequency range: 869.58675–869.64925 MHz.
Keep in mind that MeshCore may use different slots as well, even tho Narrow is the most common and widely adopted.
