150-600 - You'll never regret. Mine in on my 500 99% of the time. I shoot mostly wildlife and BIF.
Look at active D lighting - page 175 in manual. You may get some help here.
Very nice shot and background. Have never encountered that species. Wonder what there sound is like.
I can relate to your problem with my 500. 90% of the time I shoot in shutter priority set at 1000 or greater. (The 500 easily handles the higher ISO). My keeper rate increased substantially.
I usually disable VR and crank up the shutter speed >1000. Higher ISO can usually be cared for in PP. This yields more keepers for me.
Don't know the difference in weight but I've been dragging a Sigma 150-600C around for a couple of years on a 750 and now a 500. My version is very sharp on both cameras and I usually carry it with the help of a Black Rapid sling. I've considered the prime 300 with a TC, but when shooting birds and wildlife; the versatility of the zoom is priceless. You'll have a weight penalty with whatever you choose - unfortunately.
Pretty good shots around the pool at the San Luis😎
I have both the D500 and the D750 and usually carry, use, and love both. A simple answer to your question is DX for subjects, FX for landscape. You already have The DX so buy an FX to supplement. The 750 is a great camera don't underestimate it comparing it to the 500. Go with what your budget will allow 610, 750, 810 or D5. They will all deliver.
I've had the D750 for over two years now and did purchase it w/the 24-120. It is difficult not to get it w/the package because of the price. DxO Gives the Sigma 24-105 much better numbers, but it's $900 so you'd be $300 or so in the hole. I personally find the 24-120 mostly on the shelf opting for the 28-200G. It's plastic, small and light but gets great results. Since it's out of production, I found a new "old stock" for about $275 and consider it a great value. Also, like the 35 f2 for family gatherings and 50 f1.4 for sundown stuff. Neither of these will break the bank. All this said, my favorite, fun, lenses would be the Sigma 150-600 which also works well w/the 1.4 tc in good light. This is all just my personal wisdom and may or may not be helpful for you. I'm sure you will enjoy your 750 regardless of lense choices!
I've lots of lenses including the 28-200G. This is definitely my go to walk about glass. Stays on my D750 most of the time. Not bothered by the plastic.
Sigma 150-600C or S pending depth of your pockets. You won't be disappointed.
Very nice and impressive! Ought to frame this one for sure.
Did this a couple of years ago. Worthy excursion! I really enjoyed seeing
the remains of the old telegraph poles and wires.
Welcome indeed! I still have my old C3 and Argus slide projector. How about you?