Some groups of agnostics do not deny the existence of Allah, but don't accept it either. Some other agnostics accept it directly but do not feel responsible for doing anything about the fact that they were created by Allah.
Are such agnostics committing kufr?
Anyone who does not believe in the existence of Allah is committing Kufr (disbelief) as the Quran has applied the word to them:
ومن لم يؤمن بالله ورسوله فإنا أعتدنا للكافرين سعيرا
And whoever has not believed in Allah and His Messenger - then indeed, We have prepared for the disbelievers a Blaze.
Denying responsibility for doing what Allah commands is also Kufr. Satan accepted Allah, yet he became a Kafir for refusal of His commands:
وإذ قلنا للملائكة اسجدوا لآدم فسجدوا إلا إبليس أبى واستكبر وكان من الكافرين
And [mention] when We said to the angels, "Prostrate before Adam"; so they prostrated, except for Iblees. He refused and was arrogant and became of the disbelievers.
It is mentioned in the Quran in Surah Al-Ankabut (The Spider)
And when they embark on a ship, they invoke Allah, making their Faith pure for Him only, but when He brings them safely to land, behold, they give a share of their worship to others.
You can view that they know Allah only on the ship.
So the reason behind Islam is: Unification (Tawhid)and oneness
Muslims have to invoke Allah only everywhere, whatever the reason, if they know him and give a share to others it is kufr.
The second group you talked about are approving Deism and do not approve Divinity
The others are neither approving Deism nor Divinity.
In result both groups of Agnostics are committing kufr.
