Most gimbal heads are "full size", completely replace the existing head on the tripod and fit to it via a standard 3/8" stud on the tripod. (Check under the head of your Manfrotto... but chances are 95% that's what it uses, too. FYI, most Manfrotto have some set screws underneath the head that need to be loosened before the head can be removed).
What head do you have on the tripod now? The reason I ask is because a "full size" gimbal completely replaces the existing head and makes the tripod "large telephoto lens only". If the only one of those you have is the Sigma 150-600mm, then that will be the only lens you'll be able to mount on the gimbal. You'll have to swap out the head in order to use the tripod by directly mounting the camera, with other, shorter lenses. A full size gimbal head is even rather uncomfortable to use with comparatively small/light lenses like 70-200mm f/2.8s.
The reason I bring all this up, is because there are alternatives.
One I have used for over 15 years is a ballhead/Wimberley Sidkick combo. In this case, the ballhead stays on the tripod, so it can be used with any camera and lens combo. When I want a gimbal action with a larger lens, I simply tip the Arca-compatible QR platform of the ballhead to the side and fit the Sidekick to it. The ballhead gives the panning action, while the gimbal provides tilt movements. Works great! I've used it with 300mm f/2.8, 100-400mm zoom, 500mm f/4 lenses primarily. The lens needs to have an Arca-compatible plate installed on its tripod foot (but this is true with any gimbal, not just the Sidekick). I can quickly and easily swap the tripod to use with big lenses or small, with no need for tools. The ballhead/Sidekick combo is about the same weight of many "full size" gimbals too (which would end up weighing a lot more if you also carry a standard head and tools to swap out with it in the field). The Sidekick and the Kirk BH-1 ballhead I use it with easily handle a very large 500mm f/4 (about 8 lb.), DSLR with grip (2 lb.) and other accessories such as flash brackets and flash (~2 lb.).
There are alternatives to the Sidekick.... other similar gimbal adapters that aren't as expensive. The Induro GHBA costs about $50 less and is nearly identical. Movo and Sevenoak are two more brands, cheaper Chinese "clones" of the Sidekick or GHBA. The even less expensive Jobu BWG "Micro" is too small and lightweight for a lens like your 150-600mm.
However, to use any of those adapters, you must first have a fairly heavy duty ballhead with an Arca-style QR platform installed on your tripod. (Note: Manfrotto does make at least one Arca-compatible head now... But many of theirs use proprietary QR designs that won't work... While I've modified a Manfrotto ballhead by installing an Arca-style platform on it, that will add cost and may not be easily done the way some Manfrotto heads are designed.)
Take a look at the following link, which lists and illustrates the four primary types of gimbals: U-post, Single Post/Bottom mount, Single post/side mount and Gimbal adapter...
http://www.carolinawildphoto.com/gimbal_list.htmThat list is by no means complete. But it includes many of the major brands and provides good means of comparing among them.
For a more comprehensive list of what's available, see:
https://www.bhphotovideo.com/c/products/Tripod-Heads/ci/140/N/4075788769?sort=PRICE_LOW_TO_HIGH&filters=fct_head-type_1544%3Agimbal-headsIn addition to the Sidekick adapter and ballhead that I use on one tripod, I have another set up for "big telephoto lens only" with a "full size" gimbal (J/single post type with bottom mounting platform). I use the Arca QR system on all my lenses and cameras.