Does it slow down my system when I have more add-ins active?
Tools -> Add-Ins
It would be faster to have some of them active but does it affect the speed of the program as it's already quite slow on my laptop?
The best way to speed up solidworks on laptops, would be to close all other programs that you don't need and turn down the image quality and HRL quality from the options section.
Defragmenting your hard drive can have a huge effect, increasing the size of virtual memory aswell.
Last but not least, solidworks can run on even the slowest of laptops - if you have some money, upgrade your memory to max allowed, going from 1gb to 2gb of memory can speed the system up by 50%, going from 2gb to 4gb improves the speed by another 20%(32 bit windows has the memory usage barrier).