what will be performance impact if secondary server is of low configuration compared to primary server.
synchronous mode always on configured with sql server 2016 standard edition
You can probably guess at it. If the secondary server is capable of consuming 10 transactions, but the primary is consuming 11, there will be delays and waits. Now, the processing necessary for the primary vs. that for the secondary is different, so you won't be seeing a literal one-to-one as I suggested, but you must take into account the fact that with a synchronous data flow, any slow down on the secondary is absolutely reflected in the primary.