ECDHE-RSA-AES128-GCM-SHA256
ECDHE-ECDSA-AES128-GCM-SHA256
ECDHE-ECDSA-CHACHA20-POLY1305

ab -l -n 1000 -c 10 -H "Accept-Encoding: gzip, deflate, br" -Z ECDHE-RSA-AES128-GCM-SHA256 https://bytes.fyi/
ab -l -n 1000 -c 10 -H "Accept-Encoding: gzip, deflate, br" -Z ECDHE-ECDSA-AES128-GCM-SHA256 https://bytes.fyi/
ab -l -n 1000 -c 10 -H "Accept-Encoding: gzip, deflate, br" -Z ECDHE-ECDSA-CHACHA20-POLY1305 https://bytes.fyi/

error setting cipher list [ECDHE-ECDSA-CHACHA20-POLY1305]
1995798240:error:1410D0B9:SSL routines:SSL_CTX_set_cipher_list:no cipher match:ssl_lib.c:1385:

pi@pi3:~ $ which ab && ab -V
/usr/bin/ab
This is ApacheBench, Version 2.3 <$Revision: 1757674 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

pi@pi3:~ $ which openssl && openssl version
/usr/bin/openssl
OpenSSL 1.1.0f  25 May 2017

-Z ciphersuite
Specify SSL/TLS cipher suite (See openssl ciphers)

pi@pi3:~ $ openssl ciphers -v | grep ECDHE-ECDSA-CHACHA20-POLY1305
ECDHE-ECDSA-CHACHA20-POLY1305 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=CHACHA20/POLY1305(256) Mac=AEAD