Don't know much about the F19, haven't read much about the lack of depth but if owners say it is true it might be.
As a relic machine in all metal I assume the depth might surpass disc but again, no experience.
What I do have experience with is the F70, a cousin to the F75.
I have 3 Fisher coils, the elliptical concentric, the small DD sniper and the big DD F75 coil.
I also have many hours hunting in two completely different kinds of dirt...the almost perfect low mineralized Midwest type in Kansas and Missouri and the red devil dirt here in Birmingham AL. and most of my sites also have an unusual amount of extra iron mixed in.
GB numbers in Kansas averaged in the 40's to low 50's with maybe one bar on the dirt meter... if that, many sites no bars at all.
In the south I can get 70'-low 80's in ground balancing and lots of time pegged out on the dirt meter at a full 3 bars.
In Kansas all my coils could get deep, the concentric and the sniper easily hit the 10" mark and even more, the big DD past that by a few inches although 98% of my deeper targets still hovered about 6-7"...but not all.
Here in the SE. I have worked hard to get as deep as possible because there seems to be a wall here at 5" in the red stuff that prevents most detectors from getting decent ID's past that point in the really bad areas, all the iron infused into lots of our soil including the darker black stuff also limits depth.
I found that I can get deeper than that and ID good targets pretty well but it took learning a whole new language and set of target behavior to do it and it surprised the heck out of me when I realized I could do this.
Curiously, all 3 of my coils can reach about the same depths down to about 8" so far with pretty accurate ID info, deeper actually on some targets but much more jumpier and those I have taken the time to dig were always iron so far.
Again I have found bucket list coins and other targets here that were severely masked and they also hovered mostly in the 5-6" depth level.
I have dug a couple of great older targets deeper at the 7-8" level also, that is rare around here but I am thrilled I have a detector capable of doing this...with practice and experience.
Using disc and not all metal I found a super worn V nickel with my sniper coil every bit of 7.5-8" deep, a friend that hunts with me sometimes and uses an E Trac looked at the coin, looked at the small coil then looked at the depth of the hole I found it which was still opened and just shook his head in amazement.
I don't dig all targets to find these things, far from it, so I just worked on figuring out how to recognize and target the better, more higher percentage signals if I am digging deeper holes and I still get fooled by iron from time to time, deep pull tabs once in a while too, but for the most part I have been much more than successful than I thought possible but it did take some effort to learn how.
Well worth the time spent as far as I am concerned.
The F19 has all those cool features like iron audio, V break plus that higher frequency which I don't have but I still figured out settings and techniques to hunt in all kinds of sites including massive iron and find all kinds of great targets from low to high on the conductivity scale...gold to silver included.
If you are interested in Fishers the F70/F75 platform might be something to put on the list to consider also.
The T2 is another cousin built on the same platform but with a much larger adjustable iron range and slight programming tweaks and a different VDI numbering scale...but similar.