Hi danielzr, welcome to the MetaGeek community and thanks for your post! Everything you describe is becoming increasingly common in the 5GHz band, which is a big part of the motivation for opening up the 6GHz spectrum for WiFi use in the near(ish) future. But I digress.
The great news, in your situation is that 5GHz channels don’t have the partial overlap that plagues the 2.4GHz channel scheme. In 5GHz, an 80MHz channel is just two 40MHz channels being used at the same time, and a 40MHz channel is two 20MHz channels being used together. This means that any access point using overlapping channels, whether 20, 40, or 80MHz wide, can understand the control and management packets of the other devices using the same channel, and they can coordinate to share the airtime fairly, and maximize the effective performance of all devices sharing the channel.
If you know about the usage level of the different networks, you can make an informed choice about which ones you are willing to cohabitate with on a channel. InSSIDer will tell you about the utilization and the number of clients on each network, if the access points (routers) report that information. Pick the channel with the fewest number of networks (SSIDs, APs) and clients, and generally, the lower the utilization the better, though that can fluctuate pretty dramatically over time.
As to the channel width, if you have a WiFi 5 (aka 802.11ac) access point, I would stick with 80 MHz, as the access point will automatically use the narrower channels when that’s the best option and the wider channels when the channel conditions allow for the best performance benefit.