@DCDguy, adaptive resync *should* automatically throttle the resync to avoid too much, however, this is going to do this based on disk metrics where it is possible that the network to/from the node in question is being saturated.
If this is the case then you could just set the resync throttle on just the newly added node to lower the bandwidth used for resync traffic and smooth the IO (e.g. 128Mbps below):
# esxcli vsan resync throttle set --level=128
