I am creating a jump point defense base, it will have no engines of it's own so it is immobile, so to move them once constructed I am developing a tug ship
I then realize I have no idea how tractor beams work,
does the tugs speed become reduced by the more massive base once it's tractoring it? I think this might be how it works, thus like in the real world it would have an extremely overmuscled amount of engines. I hope that's how it works, otherwise again please help.
Yes. You only need 1 tractor on a tug. It can only attach to 1 ship (through the miscellaneous tab on th F6 screen). Putting more tractors on does NOT let you tow more ships. The speed is calculated as (SumOfEnginePowers)/(SumOfMasses) of the two ships, where EnginePower/Mass is the speed of a normal ship. Note that after you've connected the two ships, you need to hit the "max speed" button on the F12 screen twice
(tiny bug there) - the first hit recalculates the max speed, the second sets the actual speed to the max speed.
I tend to put about twice as many engines on a tug as I would on a normal ship of the tug's size. I also have been pretty much making only commercial-engined tugs since commercial ships got huge - most of the "speed 1" stuff I make is commercial, and a commercial tug can still tow a military ship, albeit (possibly) a bit slower than a military tug would.
EDIT: What are you planning to arm it with? Missiles? That could be bad if they jumped in right on top of you....