Correct way to config hvn_tx_queue_size

Just need a quick confirmation, in S140/SDK15.2, what is the correct to config hvn_tx_queue_size? 

I found in some post said it can not be set directly, instead one should only change NRF_SDH_BLE_GAP_EVENT_LENGTH.

While in other posts said it can be direct set as in here

So which one exactly should be the right way? Will change NRF_SDH_BLE_GAP_EVENT_LENGTH only work in 15.2?

thanks.