Damn, he outs down rebels and fortifies the border with Tevinter, the horror
If it was just fortifying... maybe. BUT the epilogue is clear he 'wins many victories'. Building a fort or improving a border isn't 'winning many victories', it can certainly help you win many victories. He's certainly NOT peaceful.
Yes... that's what would be called: ruling with an iron fist.
Which you said didn't happen.
He's a self-confessed warmonger.
The problem with putting down rebellions (well firstly people are rebelling) and being the strongman is that it only works for a time. You have to keep winning and keep suppressing dissent. If you stop (especially if you stop winning) then it can unravel very quickly. Especially if you don't play politics and breed dissent amongst the nobility then when it starts going wrong, you may not have any allies to support you.
We've had a number of (historical) rulers who've come a cropper in this way. In fact in this 800th anniversary year King John springs to mind!
And as this can rely (as with all three) on external support this could backfire in the long run for the inquisition (you're seen as supporting a weak/brutal/alien leader and you loose support too). And if that support is removed you are in trouble.
ALL three of them have issues:
Celene is a peacemaker ruling a kingdom that can remember a time when it had an empire and still wants it. Doesn't matter that maintaining the empire as it broke apart eventually broke the kingdom. One of the causes of the civil war is her peacemaking with Ferelden and others.
Gaspard is brutal strongman who doesn't play politics (see above).
Briala is a tenuous position - her position lasts as long as she can continue to hold sway over Gaspard (so must play the game at all times - though after a time this turns from blackmail to M.A.D.) but she's an elf AND a radical, implementing policies that perhaps Orlais is not ready for nor wants.
Celene and Briala comes with a mixture of the flaws of both Celene and Briala and Celene can no play marriage politics as their relationship is in the open (an added complication is that Briala is not an elf rather than a noble (who could bring supporters with her like a marriage effectively could)).