If a device has v3 credentials in DCR, then Campus will only use v3 for that device. If you specify a duplicate ranges, one with v3 and one with v1/v2c, Campus will opt for the v3 credentials. You can, however, have one range for v1/v2c and one for v3.
Data Collection has its own set of ranges you can configure, but this is simply for filtering which DCR devices to manage.
No, there is no way to force Campus to use v1/v2c over v3 if v3 credentials are configured. The problem with the BRIDGE-MIB is not due to lack of support, but rather with lack of SNMP context support. Most IOS switches now have this support (e.g. 3550, 3560, 2960, etc. need to be running 12.2(25)SEE or higher).
The most notable exceptions with regard to SNMP context support are the 2950 and XL series switches. These switches will never have context support since they cannot run 12.2 code.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...