You can download .step files for most things sold by McMaster-carr. F360 let’s you import directly using the product number- this includes pretty much any kind of bolt or screw you want.

Other software you might have to do so manually, but yeah.

Why do work when there’s a library right there begging to be used. (And nope, you don’t have to buy from them…. Even if that’s why they do it.)

Don't know about specifically for your use case of only caps, but all of the major parametric modelling programs have custom thread generating functions. Including FreeCad, if you want to pay $0 for it.

If you aren't fussed about the end result looking fancy, you can just make a cylinder and whack a threaded hole partially through it in about three steps in FreeCad, and just print the result.

The term you are looking for is "parametric". You might be able to find a design you need through the many 3D printing file sites using that term. FreeCAD and Fusion360 are open used but another is OpenSCAD if you are more programming savvy than modeling savvy. There are plenty of recipes for threads in there to make your relatively simple design request here.

Tons of good and free options, you just gotta pick which one looks easiest for you.

You can do some basic thread generation in tinkercad the thread generator has some options.

NUT JOB | Nut, Bolt, Washer and Threaded Rod Factory? (You'll need OpenSCAD if Thingiverse's customizer is broken again.) Not sure how many parameters it offers, but the ones you mention should be among them.