smallville is old af. i don't think any of the characters there are considered canon in the current dc tv universe. which is why green arrow from smallville isn't the same green arrow in arrow.
titans on the other hand is supposed to belong to the same universe as the other dc tv shows, they were even supposed to appear in one of the crossovers, but things didn't go through(people assume payment, since hbomax probably pays more than the cw), and the flash from the cw and the flash from the movies have interacted with each other. and since the dctv has merged their universes, that'd mean titans is in the same canon universe as the cw shows and the dceu movies
No, it isn't.
The "Crisis on Infinite Earths" storyline establishes, through brief cameos, that both
Titans and
Smallville take place on their own Earths, seperate from both the "
Arrow-verse" Earth(s) and the DCEU. The end of "Crisis" confirmed that
Titans remains on its own Earth, seperate.
We've also seen what Gotham City and Bruce Wayne look like in both
TItans and
Batwoman. Bruce is played by Iain Glen in
Titans. In
Batwoman, the real Bruce Wayne has never appeared, but when villain Hush/Tommy Elliot (previously played by Gabriel Mann) got surgery to look just like Wayne, he was played by Warren Christie. Glen and Christie look nothing alike!
And, anyway,
Peacemaker takes place in the DCEU Earth - where Bruce Wayne looks like Ben Affleck (for now) - not on the "
Arrow-verse" Earth, so having him in
Peacemaker wouldn't cause any conflict the Hawk role.