I got the impression in ENT, that the Klingons had some respect for the Vulcans. How much of that was how advanced and powerful they were is the question. "Intellectual puppets of the Federation" was later expressed as well. What Klingon comments we get about the Romulans is that while they might recognize them as formidable, it's not clear how respectable or honorable they think they are. But we should avoid treating species as one dimensional in a way we know that humans are not. In other words, there are probably mixed views.
Klingon-Romulan relations are a complicated matter. During TOS (and Discovery?) they are the best of allies, sharing technology and probably support in their anti-Federation imperialist agenda.
By the time of the Praxis explosion, the Romulans have (briefly?) become allied to the Federation, and pushed for the Khitomer conspiracy to wipe out the Klingon Empire. In twenty years, they isolated themselves from the Feds, but would continue their ambivalent relationship with the Klingons.
Up until the Khitomer incident, when they all-but declared War on the Klingons with the assistance of the House of Duras. In the thirty years succeeding, they were seen as blood enemies, with perhaps only the Dominion War offering a brief respite.
These all point to a disciplined Romulan Star Empire changing governments and objectives on a regular basis, and fits the narrative conceit that Romulans have always wanted discord in the region to prevent any one power from gaining too much control (hence their opposition in Enterprise towards the Coalition/pre-Federation being formed).
I think the Klingons have respected Romulan culture as worthy adversaries and relatively honorable in the past. If the supernova hadn't happened, I would assume that the Romulans would be shifting once more towards allying with the Klingons. In fact, that's probably what the Civil War and alliance with the House of Duras was meant to achieve.
As for the Vulcans, we learn in Discovery that they were exchanging weapons fire in 2016, 140 years prior to Enterprise. Vulcans are the epitome of honor, and there's no better way of gaining a Klingon friend than by giving him a bloody nose.
