While there is a degree of superficial similarity in appearance between the Observers and the Watchers, there is little to suggest any connection between the two groups besides the visual nature implied by their group names.
On the Surface:
- Despite their name, the Observers were dispatched through time to alter the past not simply to observe it. Their goal was to take total control of the government to alter their future. The Observers were fundamentally human albeit with some scientific modification to enhance their capabilities.
By the year 2609, the Observers had ruined the planet. To rectify this, a plan was put into place that involved going back in time and taking the planet from modern-day humans.
The first wave of Observers were the scientists. They were told that their job was to study the evolution of the Observers by witnessing key moments in history. The twelve members of the science team were not told about the plan for Invasion. They were only needed to alter the timeline in favor of their own evolution.
- The Watchers are a relatively benevolent god-like species which came into being near the beginning of the universe. Gaining a degree of unrivaled technological sophistication, they decided to help other species develop their intellectual capacities.
Billions of years ago, the technologically-advanced extraterrestrial race known as the Watchers decided it was their duty to help the universe's less advanced races. In their first such experiment, proposed by Ikor, a delegation of four brought atomic energy knowledge to the planet Prosilicus.
The Prosilicans accepted the gift, but used it to develop nuclear weapons and engaged in an auto-genocidal war. Ashamed, the Watchers vowed never again to interfere in the affairs of other races. Ikor drafted a code of ethics based upon strict noninterference and passive observation that was so strict that if another being were dying at a Watcher's feet, the Watcher would offer no aid. (REF: Watcher, Marvel Wikia)
- When the Uplifted species decided to take the nuclear technology offered to them by the proto-Watchers and instead of using it for energy, they used it for war; this caused an uproar in the proto-Watchers and initiated their non-interference ideology.
They do have one strange thing in common:
The Observers were able to view alternative timelines and had some degree of temporal awareness. The Watchers had the ability to view alternative or parallel timelines as well as having an awareness of time and the ability to traverse it!
This calculative prediction of the Observers in addition to their awareness of the two timelines caused by their manipulations of time indicated a form of temporal awareness and the ability to see close timelines and possible results in the current timeline the Observer is standing in.
The Watcher of a particular area does not just have awareness of a planet but of its timeline and nearby alternative realities/parallel universes. Marvel Comics series "What If" was dictated to the reader by Uatu, the Watcher of Earth and our galaxy, of events which may have taken place differently in an adjacent reality.
Is it possible the nature of the Observers and their physical similarity to the Watchers are somehow related, a homage or shout-out to Jack Kirby or Marvel or just a really cool idea someone wanted to shoe-horn into a show filled with culture, fan, and science fiction references? You betcha. It's probably very likely.
But very difficult to confirm.
On the Other Hand
There may be a there a common trope of dispassionate, bald observers/watchers/recordists. Observe Exhibits A-D
Exhibit A: The Observers (see above)
Exhibit B: The Watchers (see above)
Exhibit C: The Rigellians and their Recorders - In the Marvel Universe, there is a species of aliens called the Rigillians. Besides their being bald and their relatively tiny stature, they have a habit of wanting to know everything and to feed that need, they created a group of bald androids called Recorders whose job is to record anything of interest and return this information to the Rigellians.
Exhibit D: Metron (of the New Gods) - One of the strangest of Jack Kirby's creations was the New God, Metron. Metron was a super-genius where genius was commonplace. Metron's genius was thought to rival Highfather's. Metron spent much of his time in the New Gods runs gathering information to no understandable purpose until his plot was revealed. Metron's passion was information and he would go to any lengths, to deal with anyone and betray any cause if the value of the information was high enough.