Where tactics/strategies are concerned Trench > Yularen, and Thrawn considered Yularen to be a good tactician because he was able to comprehend his plans after they had been explained. So logically speaking, Trench should also be able to comprehend Thrawn's plans after they were explained as well.
I doubt Thrawn would consider Trench a good leader, though. Trench's downfall is that he lets his emotions get the better of him and makes decisions hastily as a result -- a trait Thrawn certainly does not respect.
Not entirely sure about the emotions argument, except for that of his final confrontation with Skywalker. I’m sure Thrawn would have had respect for Trench’s stealth technology tracking innovation.
But as Galan mentions, Thrawn admired Yularen, and Yularen was in awe of Trench’s efficiency and ruthlessness.
As for whether Thrawn would consider Trench to be a good leader? Probably. Maybe not. Trench’s participation in the Andoan conflict would be impressive to Thrawn, and would sympathise with his difficult rise to power. I don’t think Thrawn respected battle tactics as much as big picture thinkers though, and there’s little evidence to show Trench as a masterful tactician on the big stage.
I am fairly sure that they stated he was the most strategic of his species and that he won battles that would have been impossible without him.
This is what Wookieepedia says, but I am still looking for sources confirming it.
I think that his species thought of him as a god actually, still Wookieepedia. I never read up on the guy till today so I have some things to confirm.