My personal Trek canon is on the complicated side.
I generally accept the events of TOS as canon – minus such gems as “The Alternative Factor” and “Turnabout Intruder” – but not the visuals, which I think have aged terribly and look cheap/cheesy today. So I imagine the “true” TOS ships, uniforms, aliens, etc. looking closer to the ones in SNW, though I DO NOT consider SNW canon.
Harlan Ellison’s version of “The City on the Edge of Forever” supersedes the final episode.
TMP and TWOK are canon, but I’m on the fence regarding the remaining TOS films. I like them all to varying extent, even TFF, but I often feel Spock’s sacrifice at the end of TWOK was a perfect sendoff for the character and shouldn’t have been overturned.
The Early Voyages comic, along with the novels Vulcan’s Glory and The Wounded Sky, are all canon.
I haven’t read all of the Rihannsu novels, but I’m inclined to accept their depiction of Romulan culture as canon.
“Yesteryear” is the only episode of TAS I feel strongly enough about to consider definitively canon. I can take or leave the rest of the series.
I recognize TNG in broad strokes; there was an Enterprise-D commanded by a Capt. Jean-Luc Picard with a Data, Riker, etc. serving under him. But I have so many issues with the show that I only accept what’s necessary for DS9 to exist. None of the TNG films are canon.
I generally accept DS9 as canon, though not many of the elements I dislike about TNG that carried over, such as the depiction of Klingons. I’m not sure if I accept Jadzia’s death and Ezri Dax’s existence as canon.