If you use direct modulation, this will occupy very large bandwidth. Instead, if you pass the signal in a Gaussion filter, bandwidth will be smaller.
Normally large bandFM is difficult with varicap diodes within a VCO, reactance method is more suitable for this purpose...
1 msps is not that broad band. For a time, virtually all backhaul telephone traffic was sent on a 1 to 30 mbps FM microwave systems, usually 2FSK or 4 FSK, in the 2 to 18 GHz range.