Check out Reveni Labs spot meter. I use mine all the time when needed. It is very compact so it takes almost no room in the bag si you have no reason to leave it behind

I use HDR and find it woks well. I have to be careful in selecting the setting. +- 1 is very Suttle, +-2 is my usual outdoor but I have found with static objects and sky that +- 3 looks great. So it's all about selecting what works with the subject at hand

Hi
I own 2 645Nii and a z. I would get the 45-85 zoom. That is my workhorse lens. Pair that with the 80-160 and you will have most of your bases covered without getting too bulky or heavy. Both can be bought used and are usually not too expensive. The 33-55 is nice if you need a wide angle. You will need to upgrade to the latest firmware if it has not already been done. It gives you a red screen on the tilt screen to preserve your night vision. I have a Russian 500mm mirror lens and a 400mm Pentax lens. Both are nice but do not get the same workout as my other lens. There are Arca Swiss plates made for the 645. They have the pin to stop rotation and have a bigger surface area. I have it on all my 645's. They run about 40 US. One side effect is that if you do not have a tripod rated for this kind of weight you may need to update that.
I love the images that my 645s capture. breathtaking.

Hi
I have a k S2 and I like all the features it brings especially the rotation and tilting LCD screen. As you go through the manual it has a long list of features. I only recently updated to the KF as it matches all the features of the K S2. If you have a good K S2 I would go with that. If handles all the Pentax lenses well.

For most everyday use the global shutter is not needed. If you are photographing fast-moving objects you will get distortion unless you use a global shutter. The classic example is the propellers of an airplane where the blades look curved instead of straight. It takes more "horsepower" to read the entire sensor instantly as opposed to line by line. that will add to the cost.

I have used the classic M series 85mm f2 for years and still love the images it produces.

I always advocate using what you have before investing in equipment. If you find that feel limited take the time to see why and what will fix it. For abstract photography a zoom offers far more ways to make that image.

Hi
I have a KF. I would highly recommend this camera. Great features, handles all current lenses and older ones. The usual IBIS, weather sealing, great viewfinder, easy to set up for any kind of photography desired. I love the tilt/rotate LCD screen that I have enjoyed with my K-S2.

The lack of a flip screen is an annoyance. I use my Ref A right angle to compensate for that. It works with all the 35mm film and digital cameras. Worth finding in the used market I like the rotation and the 2x features.

Hi
I use the 120 FA on my 645N ii and z. I enjoy the results. I use Macro lens for portrait work along with macro. When using as a portrait lens I use a 1/4 black mist filter.