Say you have a TWebBitBtn on a form and HeightStyle property is set to ssAbsolute.
If you copy it then paste it, the new copy has HeightStyle set to ssAuto. It probably should not change, right?
I guess your form form.cssLibrary property is set to cssBootstrap. In that case, controls are initialized to default bootstrap settings, i.e. HeightStyle = ssAuto.
Set form.cssLibrary = cssNone if you do not want this.
Sorry, I have no idea what I'm doing when it comes to this stuff. I'm just trying to make it look like what it would in the VCL, and not having much luck. I just saw that this property is being changed when I paste it to the form. (Something was giving me an error somewhere about Bootstrap, so I checked stuff until it went away. I'm not actually doing anything with it. I'm guessing something else is.)
This is like going to get a hamburger somewhere and having to describe what condiments you want (ketchup, pickles, onions, mayo, tomato, etc) in Chinese (not knowing a lick of Chinese). 
Is there any guidance to follow in case you just want it to look as close as possible to a VCL app?
I can't get font attributes to change or any colors to change, I've figured out how to get some buttons that look ok, but it's from playing with 'btnxxx' settings in a huge list of attributes that takes 10 seconds for the dropdown to show up in the Object Inspector.