It is impossible to delve into the tripod market without knowing how much weight you have in terms of camera+lens. Part of the weight capacity rating is in the tripod legs, and part is in the stiffness of the head. A gimbal head will handle a long lens, but then it has more weight itself to hang on the legs. Note that when you are using a long lens for birds in flight, as the front of the lens goes upward, the camera end goes downward, assuming that you have the lens center of gravity over the head. You don't want to stand around for hours all bent over, so for that case it is best to have a tripod that can be raised up a little taller than your head. "Tall" is undefined.
In the past, I first made the mistake of purchasing an expensive carbon fiber tripod that was rated a little over what my gear weighed. However, later I moved up into some tremendously heavier lenses, so immediately my first good tripod was obsoleted. I made the mistake of getting screw-locks one time. One slipped, and about $9,000 worth of gear toppled over. I've stuck with flip-locks ever since.
I found it to be too much hassle to change out heads onto different tripods, so I ended up with one tripod/head system for one purpose and one for another.
BTW, there are some incredibly cheap gimbal heads on Amazon that are worse than worthless. Read the reviews.
Now I have one or two tripods that I will use around town or when vehicle-based. These go up to a 12kg rating. However, for backpacking purposes, I normally carry a flimsy little thing to cut down on weight. My current backpacker tripod weighs something around 17 ounces with QR, and it elevates up to about chest level. I'm using only a little more than one pound of camera on top. By using a ballast bag, I can get it stable for a 5- or 10-second shutter, but that would be mostly for a sunset scenery shot. For wildlife, I can't be waiting around that long, so I generally shoot hand-held and depend on the Image Stabilizer magic.
–B.G.–