One of the main reasons for me to switch to the Sony mirrorless system back in 2015 was the reduced size and weight of their cameras. I have small hands and and holding a heavy camera in front of my face for hours just sucked. I really used to work with monsterous cameras like a Canon 1ds MKIII which was my working horse for many years. Not to speak of a bulky Phase One medium format camera.
For almost five years, things have changed for me. I go lighter now with my Lowepro ProTactic 350AW backpack. It is tiny enough to fit under a seat on a plane which is a huge advantage for me. And it still fits all the gear that I need for my projects and when being on the road.

Like in every photo bag, you can adjust the inner dividers according to your needs. I keep the camera at the top, so it is protected the best. There's a hard shell on the top of the backpack, therefore nothing can destroy the display of the camera.
I am not a fan of the side pockets that allow access to the gear from the side, but as this is not a camera bag review, I will continue to talk about what I carry with me.
I work with fixed focal lenghts all the time. And I decide not to take more than three focal lengths when traveling. So, depending on the job, I make my choice. For shooting nudes, I take my Zeiss Batis 85mm f/1.8, my Sony Zeiss 55mm f/1.8 and the tiny yet great Sony Zeis 35mm f/2.8. Those lenses work excellent, even on the 61 MP resolution of the new Sony a7 RIV.
Body-wise, I have the Sony a7 RIV and my old a7 RII as a backup in my bag. As they have different batteries, I have to carry two different sets. This sucks, but as luck would happen, I never needed to use the backup gear, anyways (knock on wood). It really travels with me only as a backup. It's not a second camera that I use.

The new batteries of the a7 RIV are really nice. One battery takes me almost through an entire day. And this includes filming as well. But as you never know, I have three spare ones in my luggage as well.
Speaking of backups, I also have a second Sony charger with me. Just to re-charge faster (one loading cycle takes around 2.5 hours) and to be on the safe side as you cannot buy a charger on a remote island.
I work with a brand new Apple Macbook Air. It is equipped with 1TB SSD harddisk and 8GB of RAM. Except for Capture One and Photoshop, I don't run any additional software on it. Before every job, I delete all data, so I really travel with a sort of empty harddrive to be able to copy all photos and videos to the computer.
I bought the new Sony Tough SD cards. They are a bit more pricey, but said to be very stable and they are super fast. This is a huge time saver. With the Sandisk SD drive for USB-C, I can copy a full card in less than 10 minutes onto the computer. Sometimes it even takes only three minutes or so, but I guess the card wasn't full then.
Besides that, there's a little bag with my Sony lavalier microphone and connector which is a lovely piece (I reviewed it in an older blog article here). And I forgot to pull it out of my backpack for this picture, but there's also an external harddrive, so I always have three copies of the produced data from every job.
I keep the SD cards inside a tiny, sealred plastic bag in my pocket when they are full and they will rest there until I get back to my office. This helps me to make sure, I never lose any data. Even if the backpack gets stolen. Another copy is on the harddrive of the Macbook. And a third copy is on the external drive. Recently, clients also asked me to upload photos before I get to my office. This would mean, they have the fourth copy of the data. No worries about losing data any longer.
The mini tripod called T-Pod is always with me as well. And there's room for a GoPro Hero4. Quite an old GoPro, but it does the job for filming a timelapse or something. Additionally, I have a set of lenses and glass to hold in front of my lens when photographing to create those blurry effects, I often do.
Inside the backpack, I carry a pen, paper (e.g. contracts) and useful stuff like rubber hair-bands, because some models forget to bring them on set.