They are adequate as Coast Guard cutters, and suitably armed for that job. Even have some ASW capabiliity if German U-Boats show up off the east coast. Large helipad for search and rescue operations.
By the numbers, the Independence class is about the same lenght as a WMSL or a WHEC, roughly twice the beam, about 1/3 faster, significatly smaller crew, equivalent firepower.
Shorter range, but that shouldn’t matter for coastal interdiction. Smaller crew should mean lower burden for the taxpayers.
The LCS class is better fitted for the scrap yard then active duty - the maintenance costs alone are huge - not to mention any fixes to the ill-thought out class. The Treasury is ill-suited to the CG as it is and adding multi-billion dollar junk ships is just insane.
AIP subs are fine ... if you could convince the Navy they are some sort of cool super expensive toy, that being non-nuclear is a good thing, along with being built in a foreign yard.
German U-boats haven’t been seen since WWII other than resting on the bottom, but some of the smugglers underwater boats ought to be sonar visible - assuming WMSL and WHEC sonar suits have not been upgraded since the 1940s, which I very much doubt.