Ive used the a6400 since launch and honestly you are better off sticking with the official Sony gear if you want zero lag. Third-party stuff is okay for a bit but usually ends up in my junk drawer after a few months because the connection drops.

• Sony RMT-P1BT Wireless Remote Commander: This is the one I actually use daily. It uses Bluetooth so you dont need line of sight. I can trigger it from my pocket or while standing behind the tripod. Its weather-sealed too which is nice for landscape stuff.
• Sony RMT-DSLR2 Wireless Remote Commander: This is an older infrared model. It works but you have to point it directly at the front of the camera. Its cheaper and has more buttons for playback, but feels a bit clunky compared to the BT version. The RMT-P1BT is definitely worth the extra cash for portraits. It is faster to pair and way more reliable when you are out in the field and dont want to fiddle with settings.

I use Foto&Tech IR Wireless Remote Control, works well most times.

Ngl I am totally in the same position right now. I've been hunting for a solid remote for my a6400 for months and it's surprisingly hard to find something that isn't junk. Honestly, most of the third-party ones I've tried feel like they're gonna break if you look at them wrong. I've actually resorted to using a custom trigger rig I hacked together from some old shutter cables and a spare grip because I'm so picky about the tactile feel. It’s a bit of a DIY mess but it works for my portrait setups. If you're tired of messing around though, just stick with any of the Sony branded ones. Their stuff just fits the ecosystem better and you wont be fighting the connection settings every five minutes like I do with the cheap stuff. Good luck with the search, it's a bit of a rabbit hole lol.

Building on the earlier suggestion, I definitely agree that reliability is everything when you're out in the field. I've had a similar journey with my a6400 where I tried to save a few bucks on those generic infrared triggers, but they were so finicky... they basically stopped working if I wasn't standing exactly in front of the sensor. I remember missing a perfect sunset shot once because the remote just wouldnt fire from where I was standing. I eventually moved to a bluetooth-based setup like the one mentioned, and honestly, I'm so happy I made the switch. The performance is night and day compared to what I was using before. No more lag and no more worrying about line-of-sight. I've been using my current setup for almost a year now with zero complaints, and it hasnt dropped the connection once. It gives me so much peace of mind during portrait sessions when I need to step away from the tripod to talk to my subject. If you want something that just works every single time, sticking with a solid wireless connection is really the way to go... it's definitely worth the extra bit of money for the peace of mind.

SmallRig Wireless Remote Control, https://www.bhphotovideo.com/c/search?Ntt=SmallRig+Wireless+Remote+Control+Z30+3902&BI=8941&KBID=10361&SID=12345&DFF=d50

Check out the JJC Remote Commander. It plugs into the USB-C port on the a6400. The remote is very basic with just shutter and video record buttons, but it gets the job done for self-portraits and remote shooting. The cord is plenty long enough for my needs at about 5 ft. It's not fancy but it's cheap and functional. Just make sure to set the USB connection to "Remote Control" in the camera settings.

Posted by: @moke2223

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I use Foto&Tech IR Wireless Remote Control, works well most times.

Yes, it is a good wireless remote control.