My info may be out of date, but it may still work in this case.
For several years, I hit the road with an iPad 2 and a Nikon D800. Shot only raw files and simply used a USB 3.0 cable and adapter. For redundancy, I shot my cards only once and downloaded to a Hyperdrive.
My goal was to save weight and bulk during my travel. At the time, my iPad was the largest I could get, 128GB, and my Hyperdrives were designed to interface with my iPad.
I didn't use LR, just Apple photos for minimal processing. The iPad allowed me to check my photos along the way, cherry-pick images I could email and post to social media and I could carry my portfolios with me conveniently.
This worked great for about 3-4 trips. However, there were major issues.
The USB connection to the D800 was always quite fast and Apple Photo handled the files just fine. For my needs, I didn't need to spend a bunch of time editing and the output for my use at the time was fine.
However, I added a card reader and started shooting M43 for my street work.
Here's where things started to get bogged down. Whenever I'd make the connection, Photos would start from the start of the card and render thumbnails from the start, each and every time. Though the downloaded photos were checked-marked, it still wanted to thumbnail all the images. The limited space in the iPad was another issue along with once home, having to reprocess the files from the originals. The storage on the iPad was also an issue. One evening, I started to download from a half-filled 64GB card. An hour later as it was still downloading thumbs, I bumped the connection and the iPad suffered from amnesia...
I've also used a CamRanger as a wireless device to control and download from my D800 though an ad-hoc network.
Since my workflow doesn't use LR, I can't share any insight.
After the "amnesia" with and the long waits for thumbs, in addition to needing faster/better editing capabilities and also adding motion to my mix, the iPad got replaced by an iPad mini for my portfolios and now I drag along a MBP 13, i7 with SSD, SD slot and the current Photoshop CC. Though it's more weight and much larger, it's a time saver and much more practical solution to my travel needs.
Much of my travel work is now captured using M43 so at least the camera & lens weight and bulk is less than the Nikon system! I think that my present system can transfer wirelessly, but rather simply download from the cards for simplicity.
Maybe now that the iPad Pro is now bulked-up with more storage and power and Abobe has a version of Photoshop that will function on it, I may need to give the new tech a try!