well, in a simplistic way, yes.
the only difference I have made between the sfc3 and sfc2/OP models is the hardpoint placement.
all the glows are independant of the mod file.
Still, if we want to dig deeper, there is actually 2 structural differences between sfc3 and previous SFC releases, and that is called dynamic level of detail or LOD and texture formats.
What does the LOD means to the player?
In a sense that in sfc2/OP mod files there is information relative not to one but normally 3 different variations of the same model, each one more complex. For ease, and using my model as an example, in a pure SFC2/OP release there should be a vorcha with very low poly count, that would be displayed at distances where it is almost impossible to see any detail apart basic form, a medium detailed vorcha, that would be displayed by the game and medium distances, and finally a high/complex vorcha, that would be the one seen when the player is controlling the ship or almost at blank range.
In sfc3 nevertheless, there is only 1 model, and the game engine itself controls how the details are displayed.
so now the fundamental question is, how all this affects you... honestly I have no idea. It might be possible that mod files with only 1 geometrical model (Sfc3 planned) can slow your game down, or at least some years ago they would, but current computers can probably deal with that also.
as for the textures part, sfc3 has the ability to use textures in bmp, jpeg, targa and DDS formats (and a couple more I guess). SFC2/OP doesn't. So if anyone releases a model using either Targa or DDS based textures, you might have a problem... not of the game crashing I reckon, but displaying a flat shaded (non textured model).
Eventually my next release (i hope) will use textures in DDS format.
it is possible to bypass this texture problem converting the textures formats to bmp , using shareware/free programs like yannick leons dds converter 2.x , Paint.net or , a favourite of mine due to it's simplificated batch based conversion, fastStone Image viewer.
Yet, if someone used, for example targa layered based textures to give transparency effects, those will be loss when converting to bmp format, and the sfc2/OP model will look worse than the sfc3 version, even if the geometry is equal.
Personally I preffer SFC3 (talking about the modelling aspect, even tho I also end preffering sfc3, it is better graphically, has a rela cloak system, and I hate almost all the TOS aesthetics and the heavy drone based concept, but that is another story) since it has more potential to be explored due to glows, more complex textures etc.
and yes I know all the criticism about sfc3 vs previous ones, some I agree with, some I don't. If OP had the same graphical aspect as sfc3 I would probably would preffer OP. But it doesn't, and for me looks pretty dated in graphical terms.
so in short, yes, you can use most sfc3 models in OP without problems, except perharps having ships firing from the wrong places. An easy solution is to import a standard/stock model that looks somewhat close to the sfc3 model you download, in something like milkshape 3d, deleting everything except the joints, save that as ms3d format, importing the sfc3 model, delete all the joints, merge the model with the previously saved stock joints and it is done ( you might have to tweak the hardpoint placements if you want a perfect job).
In my case I used cleeve's original hardpoint placement for sfc2/op , with a little tweaking to compensate geometrical changes. If I didn't had cleeve's original hardpoint, would have probably imported the hardpoint of a KCA or KDN model.
Hope this helps somewhat.
ps: would be grateful if you can point me out the blue textures you mentioned. thanks.