I have a D5500, so you've got me beat right from the start. Only suggestion I would make is to use a back button focus if you have that available. Our daughter used to be a diver in High school, and I would sometimes lose the shot I wanted as the camera fumbled to refocus during her dives. My experience (as little as it is) with the 3D tracking mode, is that it appears to work better if the subject is moving towards me rather than a fixed distance (such as diving).

Just curious if you have tried changing the Focus Mode setting from the "I" back button, AF-A, AF-S, AF-C, or MF Mode? May not have any effect, but another something I'd try while waiting to call Tamron.

Good Luck!

Here's another article regarding the Sigma compatibility issue. Suggested to roll back the firmware upgrade to 1.0 on your D5500.

https://www.google.com/amp/s/amp.reddit.com/r/Nikon/comments/46asc5/nikon_d5500_firmware_101_problems/

I think this is the article that Gene51 is referencing in regards to Sigma lenses.

https://m.dpreview.com/articles/2157462715/sigma-issues-advisory-on-lens-compatibility-with-nikon-d5300

The Nikon WMU app has an option to import in "Recommended" mode or VGA (640x480). If set for the lower resolution, the transfer is faster. That would be a reason for the manufacturer transferring at less than optimal quality. But this is for an Apple App and not direct to a PC/MAC. This is why I would look at both the software and the camera to see if there are size settings/constraints while transferring wirelessly. Good option for putting a hundred photos on your iPhone or iPad, not so good if you want the real image transferred to your PC/MAC.

No, there shouldn't be any quality difference in a straight transfer. If the program/camera degrades/shrinks the file size then yes it would have an effect. In regards to RAW images, RAW should be RAW regardless of what is being used to transfer the files. Big transfer time difference between cable/direct and WiFi.

A polarizing filter should help, but another take in shooting through a window can be found here by Linda from Maine: http://www.uglyhedgehog.com/t-447173-1.html

That will not work with that camera and remote. He has the options of

Single - Continous L - Continous H - Quiet Shutter Release - 5 Second Self Timer - Delayed Remote - Quick Remote

He has to choose ONE of the options, by choosing either of the remotes, he is then unable to choose continuous. He can set his bracketing mode from another menu (as he has), but when using the ML-L3 he does have to hit the button three times to get his bracketed shots.

No it does not work with Continuous H, it's an either/or option, at least on my D5500.

If you set the bracket option, you do have to push the button three times as you say, but you do have to choose the ML-L3 option to activate the remote.

I pretty much agree that it's quite busy. If your friends are happy with the busyness of the image that's great. I'd try using a healing brush and clone tool to get rid of the power lines, and possibly the propane tank by the house (that's just me, I don't like power lines, and the new transformer on the pole). I took a B&W photo the other day of a river rapids and turbulent sky. I couldn't get anything workable for my tastes out of it because no matter what I did, it was still too busy.

I have the same 55-300 lens you have. Not s big deal but that lens barrel rotates, so when you zoom in/out it should change the intensity of the polarization effect. Easily remedied by just turning the filter to get your desired effect.

I have the same setup and am curious also. Page 119 of your owners manual says the following:
The D5500 can not be used with linear polarizing filters.
Use C-PL or C-PL II circular polarizing filters instead.

Along with the ND filter and tripod combination, try a few shots also using the HDR setting in your camera. I really like the combined effect that gives on slower moving water.

I just bought a Hoya - HMC ND8 52mm Neutral-Density Lens Filter ($21.00) from Best Buy, and it seems to work good, though I think I would actually like to try something a little darker myself just to be able to get more use out of it in brighter light situations. The more expensive ones you are looking at are generally a variable design, which may be better for dialing in exactly what you want to accomplish (Not sure as I only have limited experience with the ND8).