All of the CAAN regiments were royal. So we can.conclude they had cutting edge tech.
"Cutting edge" is the point. How were wars being fought in the Star League era? what was the emphasis?
Combined Armor, Air, & Naval
so what does that translate to? look at teh order.
Combined
Armor: we have units like the Prowler, (amphib tank), a multitude of hovertank types (just peruse every TRO since 3025, plus the 2750), we've had WiGE added to the game and support vees, and some of the canon WiGEs would certainly fill the same roles that a fast cutter would fill, plus being very well adapted to a navalised role by the basic construction rules.
Air: integrated air assets seems likely, but those can be run from ground bases, or dropships just as easily (perhaps more easily) and at less cost than building a fleet of carriers that are largely non-portable, highly vulnerable, and relatively slow.
Naval: so far, we have a single Naval unit of the right vintage-and it's basically a submersible tank that weighs in at a whopping fifty tons, and was also clearly built for a very specific, narrow purpose.
For Dropships, we don't really have a canon "Modified Mammoth" of the right vintage to haul anything bigger-the Davions have one, but it post-dates the collapse of the Star League, and the Lyrans may have built larger wet-naval vessels, but those are shipped in sections as cargo and take quite a bit of time to assemble at the destination.
Two CAAN regiments accompanied Kerensky on the Exodus. I submit to you, that these were probably (Likely) to be units whose largest bit of kit, was a large WiGE designed witht he capability to drop or service medium-sized vehicles, accompanied by their integral air-wing which was likely to be land-based, and their armor formation, which was probably units made up of Prowlers and hovercraft.
This would cover the primary duties of a CAAN formation (enforcement and defense in littoral areas). what would be missing, would be the large wet-naval units they really don't have any need to possess or strategic value in the Star League era.
Technically, this would, indeed be a 'blue water' force-but the blue waters involved would be close to land, because that's where everything it might be useful to guard with naval forces would be located in the Star League era (with some operations conducting interdiction and putting the boot to the neck of swampies and coastal hillbillies, drug enforcement, and Search and Rescue.)
one of the reasons the Lyrans never built more than 13 Luftenbergs, is that they're really not very good or useful war machines, but they do cost a lot of capital for exceedingly narrow and hampered capability.
essentially, they're yachts for noblemen you want to keep away from the front while still letting them claim combat command status. at best they're impressive to a coastal raiding force, and can certainly lob shells 25 kilometers inland, but that's not very far, and being as they are floating on a hostile environment, they're exceedingly vulnerable to attack from above.
oh, and sinking.
the SLDF seems unlikely to invest significant resources into a program of building surface naval
ships, an the Clans even less so. the term "CAAN", when broken down, suggests a mobile strike arm, more akin to an actual Marine combat command in layout and structure, which precludes them from being a static emplacement (which by the definitions of interstellar war, large naval vessels would be), but with a specialist mission (land on the water part of a water world, and go a-viking on offense, conduct maritime surveillance and coastal interdiction while on defense).
these suggest a premium on mobility. (supported by the Manta's stats, combat power was sacrificed for speed).
this premium on mobility fits well with Clan tactical thinking as well. (even the Star Adders tend to field somewhat quicker designs than their proposed inner sphere opponents in any given weight class or by firepower).
Large WiGE vehicles deploying on combat drops makes sense, as does a force organized around marine landings with dropships. the available dropships fit this doctrine, and it's a doctrine that is likely to work in the Star League era and during teh Klondike era and golden century, because doctrine influences engineering. Clan doctrine doesn't run in directions that would favour large wet-naval assets, and when they do make wet naval assets, they'd be likely to focus on systems that fit with some agreed upon methodology of warfare.
hence, the various suits derived for undersea mining that branched out into the Elemental, Undine and other armors, the attempts to develop undersea 'mechs (The Peregrine's peculiar armor configuration), and a heavy emphasis on hover and air vehicles, with some remnant use of existing, proven League era designed (and most likely Wing in Ground Effect type) 'cutters' being the largest units built-because they're barely portable and most of the seas are shallow in the Clan worlds.
WiGE vehicles, you see, can outrun weather systems. large hulls really can't.
of course, now that I've said all that, they're going to drop a bunch of world war ii dreadnoughts and supercarriers on us all in the fiction, just wait, you'll see...