Customised .... the word send shivers of dread down most people spines!!
What is it, what is it based on, what can it do????
If you know that then you may be able to do something about jumping between two discrete modules. However I suspect the best you'll get is completion of one allowing starting the next based on the LMS internal rules.
On the speeding up loading, that will depend on bandwidth, the server base and the content.
The web broeser can only render the page as fast as it is delivered so you need a reasonable server to start with, the LMS also figures in this as it supplies the data.. Fast is good for example a PIII will run Moodle but it won't be very fast, a dual or quad zeon server with lots of RAM runs much faster. The data has to get to the remote PC so bandwidth is important, again more is always better. The viewing PC being reasonably modern also helps, again an old PIII/P4 will be quick enough but start tossing lots of graphics and content at the browser and it will get slower. ??Do you need to recommend a minimum standard for optimum display, probably yes is the answer.
Optimise the files you use, eg if an image will be displayed at 150 x 150 don't shrink down a 2500 x 2500 image, if it's a jpeg do you need high quality. Physical size matters, small is there faster and won't add a processing overhead at the browser to rescale or eat lots of system RAM caching the content.
Plan the pages if you don't need it chop it, be ruthless and the pages will be less cluttered and cleaner (easier to read and absorb).