OK another one I have is the writers making a race so powerful that nothing can stop them, for example the Douwd. With a single thought he not only wiped out the aliens attacking the planet he was on, but every single member of that race wherever they were.
That is just so over the top ridiculous level of power. He'd probably be stronger then the Q
Most certainly not. The Douwd (Uxbridge) couldn't fight back against Troi's empathic powers, and effectively had to drown her out. He wasn't, apparently, able to reverse time on his own or bring back the dead effectively (unlike the Q, who demonstrated that multiple times). Rishon was just a simulation that he dissolved and reformed at will, but he doesn't otherwise acknowledge her as the real thing and still suffers her loss.
His guilt over the death over all Husnock further implies that that action was uncontrolled. A genocidal accident from tapping into thought powers that he usually could not access.
The Survivor shows us a powerful being, certainly, but one with many limitations and shortcomings, both self-imposed and part of its nature. His abilities pale in comparison to the Q, and I'd say he was closer to humanity than the Continuum.
Also the Klingons were by nature a warrior race so how did they find the time to do science and stuff like warp drive?
Enterprise delves deep into the Klingon backstory of a time in recent memory (as of the 22nd century) when Klingons had not adapted the warrior ethos. The warrior caste had taken over in Kolos's youth and appears to maintain that hold throughout the TOS and TNG era, but this doesn't seem the case in centuries beforehand (this also seems implied by the "Dark Times" from DS9, the ancient era when Klingons had democracy).
Science and stuff seems to date back to Kahless's time, and probably is linked to interference from other species (the oft-theorized Hur'q being the only prominent canonical example), but not necessarily so. Discovery, and to a lesser extent, Enterprise, shows us that Klingons were early masters of time travel, in an era when other powers (Vulcans) didn't believe it existed.
I've theorized before on the Vulcan-Klingon Cold War (and Hot War?) that formed from their first contact in 2016 and subsequent "Vulcan Hellos". The timing is just perfect for the recent martialization of Vulcan culture seen throughout Enterprise (undoubtedly egged on by meddlesome Romulans). But it takes two to tango: the Klingons appeared to have upended their society as well. They ended their 1200 year Emperorship (c. 2069), they got involved in crazy time hijinks (c. 2151), and the warrior caste grew and grew, to the detriment of the others.
The Klingons aren't a natural warrior race. That is a recent development, masked in part by propaganda reshaping their history. Just like Iran hasn't always been a fundamentalist Arab State. Cultures change and shift over time, and Klingons seem more adept at changing and shifting, if I understand their history right.