I agree with Frederik's comment on your original post, using either the spline IK or bendy bones would be how I would approach the problem if you wanted to have animation control over the tentacles. For the flailing, you could parent the IK targets to empties that are randomly animated using noise/sinusoidal modifier on the animation curves or the "wiggle" ...
Is there a better way to import the files that will give me a cleaner mesh?
This is less a Blender question at this point than a Sketchup question; The import isn't making all the tris, Sketchup is. Perhaps see if there's a "quads" export option.
Assuming that isn't an option (because if it is, you can stop reading), you have two options;
1: Retopologize ...
Your example shows geometry with Subdivision Surface algorithm on top.
Subdivision Surface works with quads, and when they're not there, it transforms the geometry.
Your image shows Subdivison Surface applied on top of triangles.
To get useful answers try to ask more focused questions.
It's not really clear where exactly you're stuck.
Feel free to post as many specific questions as you need, that's what this site is for :).
To adress small technical issues:
Repair non-manifold vertices (Select > All By Trait > Non Manifold)
Align the centerline more precisely (to mirror properly)
If you want to edit freely with archimesh objects, you'd have to convert them to meshes (select your object then click object > convert to > mesh from curve/meta/surf/text) but it may compromise your archimesh tools with more complex models. Archimesh objects don't give you freedom in edit mode and most edits affect the whole mesh and/or aren't flexible at ...
I see you are using a blender version <2.80 but if you think this method can save you some time, you can always do it in a newer version and export the mesh in an earlier version.
We will use the "Weld" modifier introduced in blender 2.82 and its new "Vertex group" option. Basically the weld modifier will merge the vertices under a certain threshold ...
I tried to use Bob's script on Blender 2.80, but since a lot of stuff in the Python API changed the script doesn't work anymore.
I adapted it to the new version, you may check it here:
This is a adaptation(to run in Blender 2.80) of Bob's
script to generate a mobius strip
You may find ...